Change interprocess communication with FlexBridge (FWNX-1156)

A new IPCFramework class encapsulates the previous interprocess
communication using the NetNamedPipeChannel feature of WCF on Windows,
but introduces using Unix Domain sockets on Linux/Mono for interprocess
communication.

Change-Id: Ibcde12e09e69bf2de5e730e2d0b4dd93b77ea090