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

Reloading a UnitDefinition includes loading the current UnitState

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

- add unit-definition-menu module
- add verona module and move verona services and verona interfaces to it
  to make them available in different modules
- move the distinction of different page types to app component to make
  them available for unitDefinitionMenu component

Move KeyInputModule to the modules subfolder
Create template file for AppComponent

- Reimplement UnitStateComponent as central point to send the collected
information
- Implement ValidationService to determine the responseStatus of all
forms

This is done according to the Angular best practices and minimizes
namespace collisions when using other packages which might use the same
selectors.

Technically the selectors are not even becessary since we use an Angular
component factory to create element components but it is still useful
for the DOM element naming, for debugging purposes for example.

* Take over tasks of `UnitStateComponent`
* Manage property `unitStateElementCode`
* Removing the passing of the property `unitStateElementCode` by
the components

* `UnitState.dataparts` has property `elementCodes` property, which
stores status, value and id for FormElement
* When building a unit, the stored value is assigned to the element
when it is initiated
* Removed `UnitState.dataparts.pages`
* Removed methods initPages and addStoredValues