tests for disabled buttons, drawable addes
DisableManager added, enable/disable buttons
refactored disable button test
make DisableManager Singelton
Merge branch 'master' into 8.39P_mark_disabled_buttons
rename and move UndoRedoManager
disableButton test changed
test changed
run commitcommand on uithread
Merge remote-tracking branch 'origin/master' into
8.39P_mark_disabled_buttons

Conflicts:
	PaintroidTest/src/org/catrobat/paintroid/test/integration/CropToolIntegrationTest.java
Merge pull request #55 from Catrobat/8.39P_mark_disabled_buttons

8.39 p mark disabled buttons
Implementation: @schmidiM
Acceptance: @PeteSVS
merged master into branch and resolved conflicts