keybinding: Implement keybindings for moving windows between monitors

Currently the only way to move a window to another monitor via
keyboard is to start a move operation and move it manually using
arrow keys. We do have all the bits of a dedicated keybinding in
place already, so offer it as a more comfortable alternative.

https://bugzilla.gnome.org/show_bug.cgi?id=671054
Make tile preview a compositor plugin effect

https://bugzilla.gnome.org/show_bug.cgi?id=665758