Images are always inline and scaled down to the font size of the text 
element as a whole.

This allows elements in dynamic sections to have fixed dimensions.

Some modifications to property panel logic, to show dimension fields and
proper labels.

Only implmented in dropList and button elements.

Use a suffix button to activate color picker instead of having an extra 
form field.

Also add direct input for likert line coloring color.

The theme file is now project specific because Angular demands assets
to be part of the project.
It also differs in content: The editor theme is only applied to canvas
elements. For the player every checkbox and radio button is affected.

The components now again use the default color of 'accent'. The custom
theme now has the green as accent color and no longer primary.

This new setting makes child items space around in a row with line 
break.

Images in vertical alignment now always reserve the whole row and don't 
appear next to each other.

Use unit field of UnitService directly to detect changes.

Variable naming, reorder imports etc.

Introduce interfaces and clean the structure.

This makes for cleaner imports.

The dropListList generation is now done when things are changed via the 
section menu and no longer on element update via unit service.
Also remove some interfaces to avoid circular imports. The interfaces 
are so small and insignificant that their form might as well be 
specified at usage point.

No longer have unit as subject. Components can use the unit variable as 
is and still get updated.
This removes some listener stuff in conected components.

Was not correctly creating new instances of non-primitive values. Now
uses "JSON.parse(JSON.stringify(element))" for deep copying the element
first.

Also refactor by moving the method to the UnitService, where all ID
handling should take place.

No longer is a singleton but a normal servicce now again. The singleton 
logic was needed in the past but not anymore.

Generally only the editor needs to generate new IDs. Before there was
need to have it in common because some elements (like compound elements)
needed to generte new Elements including IDs.
Now all ID stuff is handled by the UnitService and the elements classes
are handed the fully built elements. Unfortunately this means that some
logic has to move back from classes into the UnitService. To un-bloat
the UnitService a (and in the future some more) helper class is created
for this logic.

The most important thing is, that the UIElement no longer generates
an ID when created. The ID has to be created before and passed to the
constructor.

Now correctly sets the chosen background color and additionally sets 
another (configurable) color to the selected value.

The other  variants are basically the same as filled. The only
difference is the background color, which we are manilupating anyway.
So there is no reason to keep them.

Also for the background color directive different target elements are
needed for the different appearance variants. This is now possible.
As stylings of the old appearance are kept when changing the appearance
the styles need to be removed first.
In the moment the appearance value is changed the component is not
actually changed yet and there we need to wait for another Angular
change detection cycle, via timeout.

This allows to select elements without clicking them on the canvas, as 
elements may be obstructed or not visible for some reason.

The selection logic is a bit complicated because usually only the 
overlay components are usd for selection which are also the place to 
apply any highlighting on. Here we have to find the component element 
reference from the section. Therefore the double looping 
'getElementComponent' method.

Also when an elements is selected it briefly gets z-index 100 so it is 
moved to the front and visible and manipulatable.

The value may have been null in past versions.

Delete and duplicate buttons are no longer part of the tab view but are 
always visible below it.

The given serialized properties may not conform to all UIElement 
properties. They are merely meant as a building plan; they may also 
contain outdated properties which have to be transformed when reading.

Basically a div with border properties as usual.

Create object list, when none is existent yet. Otherwise append as 
before.

Now correctly reads the value IDs of drop list elements, so they can not 
be used again.

This controls the general font size. Specific spans can still be styled 
individually in the text editor.
- The TextEditor also uses this font size as default when rendering the 
text.