This uses a special event fired only by ClozeComponent, but potentially 
future compound elements as well.
The selection service gets a special method bypassing the usual 
selection logic and just firing the selection event for the props panel.

Similar to a text element but parses the text on change an replaces 
markers with actual elements.
The text is then displayed inline with the elements.

This allows to use them in template bindings. Used in compound elements.

Improve general structure. Image situation still bad.

Since sections in dynamic mode require the "contents" display setting
the background color setting must be outsourced.
This way scroll bars are avoided.

- Images now scale up and down depending on the available space.
- The new property controls the first (column) size parameter for the 
grid. The others are fixed at 1. Decimal values are allowed for 
fine-tuned control.
This prop is passed on to the child likert-row component. It uses the 
same grid and needs this info for proper alignment with the column 
headers.
- Remove unnecessary div in likert

- List items only have a margin between then but no longer on the 
outside.
- Remove unused background color. This is set dynamically in the 
template.

This looked bad having a null value in the DOM.
16 is the default font size of the app right now.

- 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.

ProseMirror seems not to allow editing text nodes. Since a text node can 
be a child of an element being applied the bullet list to, it fails for 
that text element. It seems it was workingly correctly before. The error 
seen on the console was inconsequential since we don't want to apply 
attributes to pure text nodes anyway. This change at least removes this 
error.

Move project detection of ElementComponent from AfterViewInit to
AfterContentChecked

The explicit check for undefined ensures that the value false of a
boolean property is taken from serialized elements.

In ControlBarComponent the property project replaces the property
isAspectPlayer. It ensures that delays are used only in the player
and hints are always visible in the editor.

The magnifier is always visible in the editor

Can be used for testing

Split code into separate methods

Required to query the elementModels of all instances of this class.

Split the code into separate methods