Improvements to xenon-client README.
Improvements to xenon-client README.

Added detailed steps to build xenonc using make.

Change-Id: I4734f45683a41e0488330092aa23bf965e5de5e8

toliaqat/xenon,toliaqat/xenon,toliaqat/xenon,toliaqat/xenon,toliaqat/xenon