* undo setting overflow hidden for sections
* set display of `ElementOverflow` to block

Before not all cells could be reached in all situations.

The simply was no change listener on the input.

Also the text text is by default wrapped in a paragraph. This is in line 
with TinyMCEs default output.

This is preliminary and will be reworked in the future.

This is to prohibit editing and preserve HTML formatting.
-> Also extract template from component file because it was getting to 
unwieldy.

Consider the available space for width and height
Increase their default heights

This is to prohibit entering html in the text box. Editing text should 
only be possible via editor dialog.

New elements are now put on the current(/newly created) page or section.

Now uses an extra display value to show german labels. Internal value is 
still the same: row/column.

Remove useless methods and add comments.

The section menu (containing all former properties options and
reordering) is now shown on section hover.
- With the removal of the section edit mode the view-only elements
are no longer needed, as sections can no longer be dragged.
- The unit service now has a unified logic for moving items in an array,
being used for pages and sections. Although for pages there is an
additional regarding the always shown page.
The reorder function silently ignores nonsense reorders!
- The prompt dialog now takes the text as parameter

to prevent vertical scrollbars when using default values.
* Increase height for TextFieldElement, TextElement and DropdownElement
* Change HTML structure of TextElement

They are now modified via menu at the section and no longer via props 
panel.

This also removes all page selection logic from the selection service.

It is now always made the first when page and it is taken out of the the 
index counter. So other pages start with 1, when a page is set as always 
visible.

Sections are always the same width as the page they are on.

The element has been obstructed by the resizing droplist. This extra 
droplist is removed.
To keep the parent droplist from handling the resize drop though, the 
element itself is a droplist and cathced the drop event. It is doin 
nothing with it, because resizing is done while dragging not on drop.

Also rework selected page index to be managed by the selection service.

There is a bug in Angular and as a result Material tab elements brake 
when the underlying array is changed. To circumvent that we temporarily 
remove the tab element and add it again, which should re-initialize it.

Adding elements to other section caused the old "NG0100: Expression has 
changed after it was checked".
We now manually do change detection when we update the selection 
variable.