Integration 2020 wk51 2

MR991: Remove hack in LTE PDCP for noS1 mode  
- Removes a hack which was used when LTE PDCP was used for NR in noS1 mode

MR993: UL and DL fixes LDPC short codewords 
- Fix UL & DL LDPC decoding for short LDPC code, e.g. Z_c is not multiple of 8
- Fix DLSCH data transmission with multiple DMRS symbols per slot
- small TA fixes on OAI 5G NR UE
- Implemented CQI measurement at NR UE
- NR UE cleanup 

MR1000: doc: fix build directory in BASIC_SIM.md