-> Don't hive line-coloring input but just disable.

#558

Explicitly define a label to be shown, since the shown label is done via 
innerHTML.

- Replace throwing Errors with InstantiationErors in unit, page and
  section in strictInstantiation mode

#548

#538

#536

- Remove all Roboto files

Since there is just one font, this setting can be safely ignored. This 
is easier than sanitizing all elements.

- TextAreaElement, TextFieldElement, TextFieldSimpleElement,
  SpellCorrectElement:
  - remove property: softwareKeyboardShowFrench
  - new property: addInputAssistanceToKeyboard

#461
- This property will be used for all input assistance presets
  in the future

#456

- Add Property "hasAutoHeight"
- Add Directive AutoHeight

#382

#525

#523
- Improve sanitizing of position margins

#522

- Don't report empty reference string as invalid
- Add VideoElements to check

Not just when an older version is detected.

#511

GGB elements without toolbar aren't loaded, if this parameter is true

#511

- crossOutChecked adds line-through styling if checked. This is used in 
Cloze texts to cross out words.
- This means Checkbox is no longer a PositionedElement and does not 
validate PositionProperties

The ClozeDocument needs properly instantiated UIElements for the custom 
elements.
Instead of creating a new ClozeDocument on the basis of what TipTap is 
producing and replacing the custom parts with instances, the 
ClozeDocument is kept in place but the custom parts are collected into a 
list and changed there.

#450

The logic determined the circumstances when min and max values were 
used.
Now they are passed as they are and the CSS ruleset does the rest.