- 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

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

#558

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

#461
- This property will be used for all input assistance presets
  in the future

#456

- Add Property "hasAutoHeight"
- Add Directive AutoHeight

#522

#511

GGB elements without toolbar aren't loaded, if this parameter is true

- crossOutChecked adds line-through styling if checked. This is used in 
Cloze texts to cross out words.
- This means Checkbox is no longer a PositionedElement and does not 
validate PositionProperties

#512

- Only elements with this property are considered in the player when
determining the presentation state
- Add the registration of CompoundElements at the UnitStateservice
- Fix visibility handling of section with simple rules

- Add translations for operators
- Improve and extend the evaluation of visibility rules

Also restructure files containing interfaces.

Toolbar is a single word, therefore any capitalized letters are errors. 
No need to sanitize, since this was broken anyway.

#384

- allowReplacement (moved from element to list prop)
- originList and Index are non-optional (means placeholders have to be 
used sometimes)
- Re-introduced the dict of all DropListComponents. This is the only way 
I have found to get a reference to a DropListComponent by ID. This is 
needed for returning to origin. Origin is not actually part of the 
transaction and needs to be fetched from somewhere else. Hence the dict.

- Console statements still present for debugging.

The native browser-drag-and-drop does not work in tablets. Therefore 
back to Material which works.
Features are moved over with the exception of replacing items.

- Copy-Lists now always allow putting items back.

- Renew example files
- Update versions and notes

- Add cdk scrolling strategy to keyboard that brings overlays to
scrolling

Rules for when drop is allowed have been fixed. It is quite complicated 
and therefore a lot of explanatory comments are added.

- improved translation
- add example file

Uses external software 'MathLive'.

Distpacker issues with mathlive have been solved in a custom 
distpacker.ts in scripts-folder. This is now used instead of the 
distpacker from the npm package.

Lists with this setting delete dropped value objects. This allows 
putting items back.
(Only makes sense when used with copyOnDrop. Otherwise there can not be 
duplicate value IDs).

Also improve constructor value checks to correctly handle nullish 
booleans.

#281

This was necessary because the new text selection action of the button
is not a navigation.