Add UEContextReleaseRequest

Add UEContextReleaseCommand Message
Modify NGSetup Message Encode failed

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Develop integration 2020 week 34

The following merge requests have been included:

* MR [859] : Fixed the bug not sending MSG3
* MR [860] : FeMBMS eNB / UE End-to-End chain
* MR [866] : Improved modulation speed
* MR [872] : Improvement on CUDA GPU ldpc latency

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

# Conflicts:
#   openair1/PHY/NR_UE_TRANSPORT/nr_ulsch_ue.c

Develop integration: 2020 week 33

The following Merge Requests are included:

* MR [849] : Implement Message2 (RAR) reception for NR-UE
* MR [870] : Fix softmodem restart
* MR [871] : Fix support for MIMO in rf-simulator
* MR [873] : BUILD: fix for new API on load_softscope

- Ensure that tx slot processing is done by the time trx_write_func() gets called