Initial srsLTE support

2 tests (iperf3, ping) working against a full srs{UE,ENB,EPC} network
using ZeroMQ backend for RF (so no real RF support yet, that will come
next).

Related: OS##4295, OS#4296

Change-Id: I290c0d79258a9f94f00c7ff2e1c6c5579c0e32f4
18 files changed