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

Instead, use Textfied component with the property isClozeChild

- Units and element are now built via the factory. This ensures only the
  wanted properties are present. All others are discarded.
- Since the sanatizer is supposed to check the unit defintion version
  it is used by player and editor and therefore put in common.
  This in turn makes it necessary to put the JSON resolver settings
  in the root-TSConfig file.
- Renamed a couple of properties to have clearer names.

Set back to the default setting to prevent CSS settings to spill over 
into other parts of the application.

This removes all the classes and goes back to simple interfaces for
unit, pages etc and all elements. This makes creating them easier and
cleaner.
Things like specific needs when setting element properties and most
importantly compatibility handling is done by a special service module,
that knows all the elements and how to repair old their potentially
outdated definitions.

This is done according to the Angular best practices and minimizes
namespace collisions when using other packages which might use the same
selectors.

Technically the selectors are not even becessary since we use an Angular
component factory to create element components but it is still useful
for the DOM element naming, for debugging purposes for example.

This may destroy alignment of inputs and produce unwanted scrollbars.

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

Was not working at all before. Now the logic is much simpler with the 
use of tiptap attributes.

Was broken after previous refactoring.
The renderHTML method only works with a proper return. Don't know why. 
Therefore disregard the linter warning for now.

- Naming
- Focus after nodeview insert

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

- Give proper name
- Fix variable names
- Fix deprecated methods

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.

Highlighted (background colored) text is done with mark elements which
don't have a color and make the contained text lose the styling of the
parent span, which has the text-color property.
To solve it we simply inherit the color of the parent span.

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.

(when not set)

This looked bad having a null value in the DOM.
16 is the default font size of the app right now.