Use common log mechanism in layer 3, mapping specific macros to common ones and extending common log utilities to support specific layer3 requirements

1. Moving get_pmi into a separate file and making corresponding
changes in CMakeLists.txt.
2. Creating PHY_MEX library with functions required for the receiver
mex-functions.
3. Making necessary changes in defs_UE.h so that mex-functions
do not complain about multiple LOG_ calls.

UE directory splits, creation of UE-specific files, common UE/eNB files and extraction of UE/common components from eNodeB files. renaming of files to minimize common names across directories (i.e. defs.h, vars.h, extern.h)