Break up the code into smaller methods

to prevent unnecessary scroll bars from appearing

And having the correct grid coordinates.
Also refactored the canvas sections to be different components.

* Increase height for textarea and textfield after adding new material
styles
* Remove position for validations

* 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