- New property group for flexible layout with more options to change the 
behaviour. It is now possible to build all other operations in this 
preset.

This is a free operation type that does not render much.

#590

#588

#588

Small cells and canBeCrossedOut are property of the row as they are all 
cells or none.
Additional property 'is2DigitHelperRow' is for different types of helper 
rows: single-digit in no crossing out or 2 digits with crossing out. 
2-digit is only for the top 2 substraction rows.

#589

This holds variable names, taken from the GeoGebra applet, and uses 
those variable values in the value. This makes result analysis easier.

#579

SInce this is a non-Material element the font is not automatically 
inherited. Needs to be done explicitly.

#574

- Minuend instead Subtrahend is strikable

#571

#578

#574

#560

style used in other cloze children causes the error
':host {display:flex !important; width: 100%; height: 100%;}'

#558

#559

The former solution was affecting the selection CSS of the button. Now 
the text is moved down instead.

#562

#542

This is much smaller and the intended way for web apps.

#457
#539

The directive for dynamic backgroudn color was outdated. Directive is 
removed and problem is solved via CSS custom variable.

#561

Gridsizes were accidentally changed from array to object.

The ClozeDocument was not cloned properly. Since it is possibly 
infinitely nested, manual reconstruction is less viable.

#449

- position
- label
- icon

- Replace throwing Errors with InstantiationErors in unit, page and
  section in strictInstantiation mode

Was completely broken: not showing at all in Editor, not clickable in 
Player.

Removed pipe 'aspectInputBackgroundColor'. Replaced by more elegant 
solution via inherited background-color.

THis component was still somewhat broken after the Material update.

#541

#545

The inclusion of svg icons via the src parameter of an image tag
is prohibited in the test centre for security reasons

The CSS selector for what the element to color changed (most likely with 
the Angular Material update). Also a lower z-index is needed to not 
cover the text.

#534