Concrete exception catching in actions.

* ChangeVariableAction and IfLogicAction return true in act() method
  Formula can not be interpreted.

Refactoring of Formula interpretation methods.
Refactoring of BrickViews with Formula.
Refactoring of Actiontests with Formula.
Fix of 2 failing tests.
Language version upgrade.
Merge branch 'DatatypeString' of https://github.com/Catrobat/Catroid into DatatypeString