Issue#269

Partly fixes #269 : Couldn't reproduce erroneous behavior of object variables (rotation, size, etc). StageListener.dispose() resets all sprite (object) variables correctly.

-[x] UserVariables of all sprites are reset to 0 before start of the stage.
-[x] Remove of unnecessary save-Project Calls after finishing stage.
-[x] Minor Refactoring (UserVariable Constructor)

Test: http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-test/1047/