MR1046 : Add support for NR UL SC-FDMA up to 100 MHz

MR1053Nr : pdcp nea2 security

MR1049 : improve rfsim
-Fix a regression 
Earlier parameter reading was moved to an external thread,  
Eventually the check at the end of the main was too early, 
Declaration of  some extra parameters are now on command line
-Enhancement: 
use the rfsim as a server on UE side, so we can connect two xNB to one UE
-Simplification: 
remove rfsim flags that have been made for convergence with replay function in usrp driver, but this is useless as they changed their code
-Fix a bug in ubuntu 20.04 (now the code is ready in whole OAI)


MR1056 : Bugfix: NR BSR calculation
Fixes a bug in the scheduler for BSR calculation. 
Before, we might wrongly track the BSR of a UE and not schedule it anymore although it has data. 
Should be fixed now and improve UL throughput. 

MR963 : Nr mac multi rach global edge
-Handling of Multiple Users triggering RACH request in different RACH Occasions in same slot
-Providing Random Access Response according to RACH request

MR978 : 
We have incorporated 5G NR nFAPI into the develop branch
P5 and P7 interfaces for NR have been implemented. 
With this MR, downlink transmission through nFAPI will be possible. 
We have also made sure that 4G nFAPI can be used from within the develop branch.

1) Only count new transmission as scheduled bytes (which is then
compared against the BSR)

2) When subtracting scheduled bytes after successful reception, subtract
TBsize from correct HARQ process

go figure...

Dirty!

Dirty.

Dirty...

- a new section in the configuration file to select security algorithms,
  with new code to deal with it
- cleanup CG-ConfigInfo: specs seem to indicate that we must not
  add mcg_RB_Config; the gNB has to deal with that
- as a consequence, modify fill_default_rbconfig() that is called in
  every cases and needs security and bearer parameters

The new section in the configuration file looks like:

    security = {
      # preferred ciphering algorithms
      # the first one of the list that an UE supports in chosen
      # valid values: nea0, nea1, nea2, nea3
      ciphering_algorithms = ( "nea0", "nea2" );

      # preferred integrity algorithms
      # the first one of the list that an UE supports in chosen
      # valid values: nia0, nia1, nia2, nia3
      integrity_algorithms = ( "nia0" );
    };

The code is forced to use nea2, no matter what the UE supports.

After 2^18 PDCP packets, it will fail to work (we don't use HFN yet).

These limitations will be fixed in later commits.

The existing security function was not reused, because it does too
much memory allocation and initializes the security context at each
ciphering. So here comes nr_pdcp_security_nea2_cipher(). And also
the ciphering is done inplace. To be changed if necessary.

- compute correct kgNB
- propagate properly NR security capabilities of an UE
  (involves: rrc, s1ap, x2ap)

* add the RA process to handle to command parameters
* Do not create the RAR_pdu into an intermediate array, but directly
  into the nFAPI TX_req
* Slightly restructure nr_generate_Msg2() to first make AssertFatal()
  checks, then proceed allocating