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.

- Reordered the buttons to make it look nicer (but still make sence 
logically)
- Put some more divs with flex layouting to prevent elements moving 
unexpextedly.
- Changed color and list inputs to split-buttons. Those compone a button 
with a dropdown.
- The editor now saves the set color and  it can be applied to 
subsequent selections as well.

The icon does not make it sufficiently clear what the purpose is.

Since no default size is set, the default font size is set to 16px, 
which is the browser(?) default on my PC.

Before it was done with a dysfunctional hack. Now with proper extensions 
to existing (tiptap-node-)extensions.
Also reads existing style and sets select-element accordingly.

The main components are right at top level and the directories below
mimic the data structure (unit->page->section).
The toolbar is only used in dev mode and does not belong directly to the
unit view.
The TextEditor is a complex component and deserves it's own directory
even though it is used within the unit-view. Might be refactored to its
own module later.

Customized margins for paragraph elements.

The other one used some deprecated functionality. Also we have more 
control over what is happening now.

Based on TipTap which in turn is based on ProseMirror. No further assets 
are needed.