#610

#620

#618

#616

#608

to make them available for new trigger element

- It will be used for trigger element

#586

Making element components unclickable is now applied to all child 
elements. This is necessary because some Material-components have child 
elements with specific pointer-events settings, which makes it possbile 
to interact
with them even though the parent is not clickable.

It is also now set via class on a parent element instead of the 
component itself.

#524

This makes the controls fit better into the fieldset box.

The color buttons now use outline instead of background-color for 
showing the selected color.

Also some alignment improvement and a hover marker for the select 
button.

- and AnswerSchemeValue with VariableValue

- Remove unused imports

#599

So it moves away from the "normal" settings.

- 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

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.

-> Don't hive line-coloring input but just disable.

#558

Explicitly define a label to be shown, since the shown label is done via 
innerHTML.