- Fix type of selectedGroup

- 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

Use private methods
Define all messages as properties

Reloading a UnitDefinition includes loading the current UnitState

This facilitates the testability