Renaming constants

Fix for issues #336  and #306 
Pocket Code Directory renamed from catroid to pocketcode. As discussed we leave the folder on the current SD card directory (not in package directory because projects may be deleted there when a newer version is installed - which is very inconvenient for users).

Jenkins testrun:
http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-test/1004/