Initial work on TooltipManager and MessageManager
Some more work done on MM and TM
Merge remote-tracking branch 'origin/master' into sun-defcoding
Implemented undo function
Implemented Message classes
Merge branch 'sun-defcoding', remote-tracking branches 'origin/hyungjon-datastorage' and 'origin/hyungjon-messages'

Conflicts:
	src/application/DataStorage.java