- Simplified the code logic. Verification is done once in the beginning 
and not on every element.
- Now uses semver to verify and compare version strings

Now shows an error message and continues with an empty unit.

This may destroy alignment of inputs and produce unwanted scrollbars.

It is better to hide that abstraction in the unit service.

Better solution without an extra variable.

- This improves scroll snap behaviour
- Set background color of page
- Interpret the margin of a page as padding. What it really is

ImportModuleVersion stores the unitDefinitionType of the loaded unit
definition. During the initialization of the unit, the individual
elements can react to the stored value.

and DropListSimpleElement

Use singleton instance of IdService in UIElement