Merge remote-tracking branch 'origin/update-to-2019-march-june-release' into integration_develop-nr_2019w32

LTE-RRC 15.6.0
NR-RRC  15.6.0
S1AP    15.6.0
X2AP    15.6.0 and 14.7.0

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

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

Integration develop nr 2019w28

See merge request oai/openairinterface5g!633

adding support 3/4 sampling for 40MHz (in that case OFDM symbols are not necessarily aligned on 32byte -> segfault on AVX2 architectures)

* To run gNB : sudo ./nr-softmodem -E -O ../../../targets/PROJECTS/GENERIC-LTE-EPC/CONF/gnb.band78.tm1.106PRB.usrpb210.conf
* To run UE : sudo ./nr-uesoftmodem -E --numerology 1 -r 106 --phy-test -C 3510000000 --ue-rxgain 90 -d
* We had done a wired test with 40dB attenuator in between gNB and nrUE.

Nr ue fapi improvements

See merge request oai/openairinterface5g!618

however, I had to hardcode the parameters for the PUSCH in nr_ulsim as the fapi interface still has bugs.

This reverts commit 3574481b.

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