Added GetWindowID to the X11XCB_Window classes.
Make PrimaryWindowList a std::list for constant time addition and removal of elements.
Finished most of the tree scanning function.
Added Un/ManageWindow methods to the WindowManager class.
Moved all data from the Screen interface into the implementation.  Nothing is forced on the implementation.
Moved all data from the Window and PrimaryWindow interfaces into the implementations.  Also made X11XCB_RootWindow derive from X11XCB_PrimaryWindow and RootWindow.