- Replace top layer with inline editor
- Make keypad and keyboard available for TextAreaMath

- add packge cortex: needes for math-live

IDs can and will be generated by the element constructors.

Disallow state variables without alias.

They are registered when being created.

#713

#716

This method is the same for all elements and can be implemented in the 
parent.

#703

This may happen when changing the Clote document property.

Also move cloze-code into Cloze and no longer have it in a general 
purpose service.