Move the dummy monitor manager to his own subclass / file
Move monitor-config to its own header file
Rename monitor-config => meta-monitor-config
Rename monitor => meta-monitor-manager
Start molding out a new src/backends/ dir

Right now this just has all of the files in one directory. We'll
be introducing more structure to this in the future, and build
a proper backend system.
Move mutter-Xatomtype to x11/