- 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

Several elements were broken after updating the Material library.

Add new component for combobuttons, which allow selecting and applying a 
value in one connected element.

New character: protected dash (which does not break lines)

#455

- Set the duration of highlighting anchors to 15 seconds
- Disable simultaneous highlighting of anchors

The extension is needed to define text areas in the rich text editor
and make them available for the button component

- Make position props on buttons optional
- Move UIElement creation back to Factory instead of within Section

The TipTap editor needs a setting to be able to read base64 encoded 
images.

Also improve method name.

#297

More german quoting characters.

#209

Better icons and reordered elements.

#267

The material dialog functionality used, adding the mat-dialog-title 
directive the toolbar.

Input elements are now grouped in fieldsets.
They also a cool gradient background color.

- Naming
- Focus after nodeview insert

Also editor in cloze mode now respects the element's font size.

This dash is a bit shorter.

This a top/99/double quote.

Also reorder the special chars a bit some it looks nicer.

This is for the different use saces of a simple text element and a cloze 
element. The latter needs more inputs for child elements and also return 
JSON instead of HTML.

The NodeViews are for the TextEditor to render Angular components, which
now serve as preview instead of the old backslash escaped characters.

All extensions are now placed in a specialized directory. Except the
NodeView stuff which is kept together.

Also improve tooltips.

Correct german form: 99-66

This creates a blockquote-element, which is styled globally with 
specific quotes and alignment.

Images are always inline and scaled down to the font size of the text 
element as a whole.

This controls the general font size. Specific spans can still be styled 
individually in the text editor.
- The TextEditor also uses this font size as default when rendering the 
text.

The tooltip declarations does not need escaped text. Was shawing one to 
many backslashes.

The font size is applied by setting the list style. This is a 
workaround, since the list extension does not support setting font size 
directly. It takes the selected font size (which is now saved ina 
variable) and applies it. This is indepent of the font size of the text 
in the list. The item font size is done individually with a span anyway.

Also font size and list style droplist now (re-)apply the value on click 
of an item. This allows updating font sizes and list styles without 
having to select another option first.

- Add a new variable to save the selected font size and reuse it for 
list styles.