- 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

- Reduce amount of properties
- Split code in separate methods
- Define some properties as input properties

This eliminates the need to specify the different page types in
AppComponent

Knowledge of the 'document' existence is only a matter of the function 
not the caller.

This marks the end of the test according to the expect method