Also add release notes document.

The duplication is done by creating a new element (UnitUIElement)
for each element of the copied object. And then overwriting it with
the props of the old one, in addition to assigning a new ID.

Can now be repositioned and moved between sections properly.

- The selection service only needs to handle element selection. For
pages and sections having the index is enough.
- Those indeces are simple fields instead of observables. This also
simplifies the components which don't have to get the value out of the
observables.
- Therefore the selection service does no longer need to have a direct
reference to the unit service and it's unit.
- Selection logic is not done by the section components themselves but
by the parent canvas component.
- The unit service can now manipulate pages and section by index in
addition to passing the necessary objects directly.

* Fix scrollbar bug
* Remove using of timeout method
* Add Material fonts

Because the always visible page is now positioned at the first place of
the unit definition.

* Remove unnecessary styles
* Refactor case distinctions
* Improve styles of some elements

Refactor styles for elements and element overlays to achieve stretching
of dynamic sections when text areas are resized

Commenting the type check out for now. I suspect we might need it again.

When maxWidth is not set it now correctly ignores the prop is takes the 
default 900px.

Some of them are need while building. Also we might want to add enable 
more stuff in the future and then it is good to have the files 
available.

This was not of much use.

The external JS files need to ne put in the wrapper html so that the 
distpacker can find and merge them.
- Also delete all unused tinymce asset files.

                                                         [style.height.%]="100"

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.