Issue#269

Partly fixes #269 : Couldn't reproduce erroneous behavior of object variables (rotation, size, etc). `StageListener.dispose()` resets all sprite (object) variables correctly.

* UserVariables of all sprites are reset to 0 before start of the stage.
* Remove of unnecessary save-Project Calls after finishing stage.
* Minor Refactoring (UserVariable Constructor)

Test: http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-test/1047/

Edit: new TEST: http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-test/1048/