Issue#641

Fixes #641 
The BottomBar is now hidden everywhere where it is not intended to be, like renaming/deleting objects (instead of disabling the buttons in the Bottombar).
Also the BottomBar.java class has changed. Now there are methods for setting the visibility of the BottomBar and the Add+Play - Button. 
The Bottombar separator is now handled automatically by BottomBar.java (was: setting separator visibility manually where it was needed).


Jenkins Testrun(s):
https://jenkins.catrob.at/job/Catroid-Multi-Job-Custom-Branch/324/?

Ran the failed test separatly 5 times:
https://jenkins.catrob.at/view/Catroid/job/Catroid-single-UI-device/71/