fixed CAT-531

added try/catch to location of possible exceptions

added default case to switch statement
Merge pull request #1083 from Catrobat/CAT-531

[CAT-531] NullPointerException: LookFragment.onActivityCreated
cat-531 #fixed
fixes double entries in MainMenuActivity's setting menu, caused by merge of CAT-1055
Merge pull request #1087 from Catrobat/fixCorruptMerge

fixes double entries in MainMenuActivity's setting menu
Introduced Command.java interface Introduced CommandFactory.java and ChangeFormulaCommand.java
Refactored FormulaEditorFragment.java to support FormulaBricks
Moved OnClick method of formula bricks to FormulaBrick.java
Replaced getFormula method by getPreferredFormula method in FormulaBrick.java
Changed the bundle arguments of FormulaEditorFragment. Reference to the FormulaBrick and the BrickField are passed to the FormulaEditorFragment. Making use of command pattern to change formulas by FormulaEditorFragment.java