- Implement hasSchemerData in UIElement
- Fix nullable field for some elements

# Conflicts:
#	projects/common/models/elements/input-elements/checkbox.ts
#	projects/common/models/elements/input-elements/drop-list.ts
#	projects/common/models/elements/input-elements/dropdown.ts
#	projects/common/models/elements/input-elements/radio-button-group.ts
#	projects/common/models/elements/input-elements/slider.ts
#	projects/common/models/elements/text/text.ts
#	projects/editor/src/app/services/unit.service.ts

- Use done event of keyboard animation to set the scroll position
of the element
- In small browser views elements are scrolled to the top of the view
instead of the middle of the view

Turns out the space within the template code are doing this.

#270

More german quoting characters.

#209

There was at least one bug, where entering a number could create a list 
with wrong styles. This is the easy fix by disabling all that, instead 
of fixing it, which might bo out of our jurisdiction anyway.

#226

Better icons and reordered elements.

#267

Italics indicate that this is not a proper text.

- Missing type inforamtion as constructor parameter
- Also the new ID generation mechanism uses the type of the element to 
request an ID from the the IDManager. Here was a mismatch, where the 
type is 'likert-row', but the IDManager only knew 'likert_row'. This is 
now files all IDs use hyphens instead of underscores.

This is needed in on drop logic to set the new value.

The dragged image did contain carry information about it's element.
Also remove useless drag and drop functionality for the placeholder.

Remove 'any's be adding proper types and using 'never'.

This reverts commit da09ac1e.

- problem with nullish values

Page needs to be a partial as it is only the blueprint.

Now properly finds all normal and simple drop lists.
This is achieved by a new method of unit all it's sub-components, which 
returns all contained elements with and optional type filter.

Also improve (still not very pretty) styling of the drop list props 
panel.

#260 #259

#264

There were some cases where elements could end up without an ID.
Also just in case an error is thrown when no ID is present.