- Toggling of keyboard and keypad are now async
- Keyboard and keypad animations are disabled for a short period of time

- Input field manipulation moves from service methods to new
  TextInputGroupDirective

- and AnswerSchemeValue with VariableValue

- Remove unused imports

Windows convertibles were not recognized as mobile devices by this check

#599

- Now every element can overwrite 'getAnswerScheme' of 'UIElement'

- Method is already defined in superclass

#583