Two implementations are provided:
* Amarisoft Ctrl interface (websocket)
* Mini-Circuits Programmable Attenuator (HW, HTTP API) [1]
in Amarisoft ENBs, if no rfemu is configured explicitly, the Ctrl
interface one is used by default, while still being possible to use the
HW one.
[1] https://www.minicircuits.com/pdfs/RC4DAT-6G-60.pdf
Change-Id: Ie98a3fb9bcd2b87b96ecbb5b79e0f53981892a32
