#667

#656

#582

#606

#605

#608

- Prevent input of 'Dead' keys

- Input field manipulation moves from service methods to new
  TextInputGroupDirective

- Remove all Roboto files

Since there is just one font, this setting can be safely ignored. This 
is easier than sanitizing all elements.

#528

#461

#461
- This property will be used for all input assistance presets
  in the future

#397

- Use own StateVariableStateService which uses the same new base class
as UnitStateService

#401

- Only elements with this property are considered in the player when
determining the presentation state
- Add the registration of CompoundElements at the UnitStateservice
- Fix visibility handling of section with simple rules

- Basic implementation

Most importantly remove the standalone switch and let the service always 
send postMessage, even when there is no surrounding application 
listening. This helps testability and has no downsides.

Also:
- Make methods static where applicable
- Remove useless variables and methods
- Improve variable initialisation (to allow undefined)