Added GUIMapEvents Container script and Blank Sprite Object for it

Has small state machine to handle type of GUI to use according to
MapEvent.
Merge pull request #26 from jajav33/master

Added GUIMapEvents Container script and Blank Sprite Object for it
Fixed prefab reference.

Fixed it for real this time.
Also fixed the remnants of it on the MapEvent class.
Merge pull request #27 from drobbs/master

Fixed prefab reference.