#606

#608

#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

- Replace type 'any' with 'unknown'

Level 2 is now the level with mild logging. Level 3 does not log 
anything apart from warnings and errors.

- A HotspotImage has an image and divs placed on it, which are used
as hotspots
- Inherits from FormElementComponent, which is why the hotspots are kept
  as a list in the value property.
- Can be validated as required and uses its own custom validator

- problem with nullish values

- Improve tests
- Change log level logic
- change default log level

- Disable explicit any rule, because here the native interface of
'window.console' uses 'any[]'

- default log level is 1 (logs are not displayed,
but info, warn and error)
- uses its own logging module
- add path to logging module in tsconfig