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.

Elements can be dragged from the toolbox and will be placed where they
are dropped.

This is done by HTML drag and drop instead of Material dragNdrop. This
is because the setup is a lot easier and uncomplicated. In the future
the other Material drag and drop may be refactored away completely.

This is causing a bug, where elements can not be properly dragged to the 
top or left. I don't know why that happens. It may be a cause of to many 
nested divs with positioning statements.

This enables to hightlight parts of the text with colors.

Clearer structure of methods and parameters.
Also some more stuff regarding the switch from angular-editor to 
tinymce.

The old one has bugs, like not setting background color. It also relies 
on deprecated API features, which may stop working any time.
TinyMCE did not exhibit any bugs so far.

This is the basic installation. rework of the whole DialogService and 
it's editors follows.

This uses kolkov/angular-editor.

The known bug of number fields not emitting number but strings, which 
destroys the model (values).
Those fields were forgotton before.

Ticket: #51

Material cdkDrag elements interfere with dynamic styling. It needs an 
extra div, which was mistakenly removed.

To make it work that the section itself can handle drop events, but
also have the canvas to handle drops when outside of the section, all
the allowed dropLists have to be connected. Because the lists are not
properly nested (see below), this needs to be done manually by IDs.
This list is given to the necessary dropLists to make it possible to
drop items not only into them but also any other connected dropLists.

Dynamic sections have droplists for the grid cells next to the actual
elements. Elements can not be children of the grid cells because they
can span over multiple cells.

Dynamic sections don't have a general drop area, like static sections.
They have grid placeholder elements which are droplists. Therefore they
have no parent dropList to add to the list but themselves.
Static elements only have the parent, which is added to the list.

Resizing in dynamic sections is handled by the section/element-overlays
themselves.

Ticket #38

The button is hidden when there is only one section. There always has to 
be at least one section.

Ticket: #35

The urls must be declared as trusted to be accepted by the application.