When elements are dynamically positioned there is no space below the elements

Getter work like functions and are executed every time Angular change
detection runs.

Refactor some translations

* Move setting of validators from `FormElementComponent` to
`ValidationMessageComponent`
* Add validators and warnings to `ValidationMessageComponent`
* Move subscriptions for form controls and their validators from
`PageComponent` to `FormComponent`

* When creating components for each element a
`ValidationMessageComponent` is also generated dynamically
* Prepare usage of default values for form elements
* Add `form.ts` for form specific interfaces
* Rename some variables and properties