Merge branch 'master' into testAdditionalMathFunctions

Conflicts:
	catroid/res/values-de/strings.xml
	catroid/res/values/strings.xml
	catroid/src/org/catrobat/catroid/formulaeditor/FormulaElement.java
	catroid/src/org/catrobat/catroid/formulaeditor/Functions.java
	catroid/src/org/catrobat/catroid/formulaeditor/InternFormulaKeyboardAdapter.java
	catroid/src/org/catrobat/catroid/formulaeditor/InternToExternGenerator.java
	catroidTest/src/org/catrobat/catroid/test/formulaeditor/ParserTestFunctions.java