Adapter for using multiple master-slave protocols

This work was done as part of my GSoC 2013 project with huge help of Dustin Mithell, Tom Prince, Jared Grubb and John Carr.

This pull consists from 2 parts.
Adapter presents additional layer between protocol implementation and high-level logic.  It's provides interface which could be realized to support different protocols between master and slave.

Another part is implementation twisted Perspective Broker protocol which uses this interface with fully compatability with old slaves.