update documentation and improve help text display

common/config/DOC/config.md

 # OAI configuration module
 
-The configuration module provides an api that other oai components can use to get parameters at init time. It defines a parameter structure, used to describe parameters attributes (for example name and  type). The same structure includes a pointer to the variable where the configuration module writes the parameter value, at run time, when calling config_get or config_getlist functions. For each parameter a function to check the value can be specified and pre-defined functions  are provided for some common parameter validations (integer in a range or in a list, string in a list).  The module also include a mechanism to check that no unknown options have been entered on the command line
+The configuration module provides an api that other oai components can use to get parameters at init time. It defines a parameter structure, used to describe parameters attributes (for example name and  type). The same structure includes a pointer to the variable where the configuration module writes the parameter value, at run time, when calling config_get or config_getlist functions. For each parameter a function to check the value can be specified and pre-defined functions  are provided for some common parameter validations (integer in a range or in a list, string in a list).  The module also include an api to check that no unknown options have been entered on the command line and a a mechanism to display a help text for suppoted parameters.
 
 ## Documentation
 

common/config/DOC/config/devusage/api.md

 ```c
-configmodule_interface_t *load_configmodule(int argc, char **argv)
+configmodule_interface_t *load_configmodule(int argc, char **argv, uint32_t initflags)
 ```
 * Parses the command line options, looking for the –O argument
 * Loads the `libparams_<configsource>.so` (today `libparams_libconfig.so`)  shared library
 * Looks for `config_<config source>_init` symbol and calls it , passing it an array of string corresponding to the « : » separated strings used in the –O option
 * Looks for `config_<config source>_get`, `config_<config source>_getlist` and  `config_<config source>_end` symbols which are the three functions a configuration library should implement. Get and getlist are mandatory, end is optional.
-* Stores all the necessary information in a `configmodule_interface_t structure`, which is of no use for caller as long as we only use one configuration source.  
+* Stores all the necessary information in a `configmodule_interface_t structure`, which is of no use for caller as long as we only use one configuration source.
+*  if the bit CONFIG_ENABLECMDLINEONLY is set in `initflags` then the module allows parameters to be set only via the command line. This is used for the oai UE.
 
 ```c
 void End_configmodule(void)

common/config/DOC/config/rtusage.md

@@ -27,6 +27,63 @@ $ ./lte-softmodem -O libconfig:<config>:dbgl1
 ```bash
 $ ./lte-uesoftmodem -O cmdlineonly:dbgl1
 ```
+To get help on supported parameters you can use specific options:
+*  ---help: print help for command line only parameters and for parameters not defined in a specific section 
+	*  ---help_< prefix > : print help for parameters defined under the section < prefix >
+
+```
+./lte-softmodem -O libconfig:/usr/local/oai/conf/enb.nbiot.band7.tm1.50PRB.usrpb210.conf   --help
+[CONFIG] get parameters from libconfig /usr/local/oai/conf/enb.nbiot.band7.tm1.50PRB.usrpb210.conf , debug flags: 0x00000000
+.............................................
+[LIBCONFIG] (root): 19/19 parameters successfully set, (16 to default value)
+
+-----Help for section (root section)            : 019 entries------
+    --rf-config-file: Configuration file for front-end (e.g. LMS7002M)
+    --ulsch-max-errors: set the eNodeB max ULSCH erros
+    --phy-test: test UE phy layer, mac disabled
+    --usim-test: use XOR autentication algo in case of test usim mode
+    --emulate-rf: Emulated RF enabled(disable by defult)
+    --clock: tells hardware to use a clock reference (0:internal, 1:external, 2:gpsdo)
+    --wait-for-sync: Help string not specified
+    --single-thread-enable: Disables single-thread mode in lte-softmodem
+    -C: Set the downlink frequency for all component carriers
+    -a: Channel id offset
+    -d: Enable soft scope and L1 and L2 stats (Xforms)
+    -q: Enable processing timing measurement of lte softmodem on per subframe basis 
+    -S: Skip the missed slots/subframes 
+    --numerology: adding numerology for 5G
+    --parallel-config: three config for level of parallelism 'PARALLEL_SINGLE_THREAD', 'PARALLEL_RU_L1_SPLIT', or 'PARALLEL_RU_L1_TRX_SPLIT'
+    --worker-config: two option for worker 'WORKER_DISABLE' or 'WORKER_ENABLE'
+    --nbiot-disable: disable nb-iot, even if defined in config
+    --noS1: Disable s1 interface
+    --nokrnmod: (noS1 only): Use tun instead of namesh module 
+--------------------------------------------------------------------
+
+[LIBCONFIG] (root): 4/4 parameters successfully set, (4 to default value)
+
+-----Help for section (root section)            : 004 entries------
+    -R: Enable online log 
+    -g: Set the global log level, valide options: (4:trace, 3:debug, 2:info, 1:warn, (0:error))
+    --telnetsrv: Start embedded telnet server 
+    --msc: Enable the MSC tracing utility 
+--------------------------------------------------------------------
+
+[LIBCONFIG] loader: 2/2 parameters successfully set, (2 to default value)
+[LIBCONFIG] loader.telnetsrv: 2/2 parameters successfully set, (1 to default value)
+[LOADER] library libtelnetsrv.so is not loaded: libtelnetsrv.so: cannot open shared object file: No such file or directory
+Getting ENBSParams
+[LIBCONFIG] (root): 3/3 parameters successfully set, (1 to default value)
+
+-----Help for section (root section)            : 003 entries------
+    --Asn1_verbosity: Help string not specified
+    --Active_eNBs: Help string not specified
+    --noS1: Help string not specified
+--------------------------------------------------------------------
+
+/usr/local/oai/issue390_configmodule_cmdlinebug/openairinterface5g/common/config/config_cmdline.c:224 config_process_cmdline() Exiting OAI softmodem: [CONFIG] Exiting after displaying help
+
+```
+
 For the lte-softmodem (the eNodeB) The config source parameter defaults to libconfig, preserving the initial -O option format. In this case you cannot specify the debug level.  
 
 ```bash

common/config/config_cmdline.c

@@ -290,4 +290,5 @@ int config_process_cmdline(paramdef_t *cfgoptions,int numoptions, char *prefix)
   }   /* fin du while */
 
   printf_cmdl("[CONFIG] %s %i options set from command line\n",((prefix == NULL) ? "(root)":prefix),j);
+  return j;
 }  /* parse_cmdline*/

common/config/config_userapi.c

@@ -178,7 +178,7 @@ void config_printhelp(paramdef_t *params,int numparams, char *prefix) {
     printf("    %s%s: %s",
            (strlen(params[i].optname) <= 1) ? "-" : "--",
            params[i].optname,
-           (params[i].helpstr != NULL)?params[i].helpstr:"Help string not specified");
+           (params[i].helpstr != NULL)?params[i].helpstr:"Help string not specified\n");
   }   /* for on params entries */
 
   printf("--------------------------------------------------------------------\n\n");