Added Mudblood.Contrib.MG

Basic MorgenGrauen Support:
- Combat coloring and fitness values
- State
Move re-export of (>=>) to Control.Trigger.Monad
Mudblood.Contrib.MG: Added Mapper modules.
Mudblood.Screen.Gtk: Fix non-exhaustive pattern in execUIAction.
Mudblood.Contrib.MG.Mapper: Define roomTriggers as stateful trigger.
Mudblood.Contrib.MG.Mapper: Move mapperLastLine from global scope into
the state of roomTriggers.
Gtk UI: Remove 'label' default labels.
Mudblood.Screen.Gtk: Added menus.