base: split out the VncServer into a VncInput and Server classes

base: split out the VncServer into a VncInput and Server classes

This patch adds a VncInput base class which VncServer inherits from.
Another class can implement the same interface and be used instead
of the VncServer, for example a class that replays Vnc traffic.

--HG--
rename : src/base/vnc/VncServer.py => src/base/vnc/Vnc.py
rename : src/base/vnc/vncserver.cc => src/base/vnc/vncinput.cc
rename : src/base/vnc/vncserver.hh => src/base/vnc/vncinput.hh