synching with the latest version of the mirage-net code
adding merlin project file
extract a portion of the ocamlgraph library and adding as a standalone in order to allow compilation for xen backend
splitting openflow functionality in 3 sublibraries
fixed unix-socket backed compilation
documenting and cleaning code for the switch module
decouple from the controller connect method the controller callback initialization
fixing the build mechanism
adding documentation and cleaning the controller code
documenting the openflow socket module
fixing ofswitch_config code
documenting flowvisor topology module and lldp parsing module
adding comments on flowvisor interface
flowvisor cleaning up the code of the flowvisorw
fixing unix backend example code
fixing support for unix backend and cleaning up library code

Merge branch 'feature/fix-unix-direct' into mirage-synch
fixing xen examples
removing old files
fixed examples using the openflow library and running over xen.

Merge branch 'feature/xen-backend' into mirage-synch
fixing port removal on unix-direct and fixing the build files