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

This was changed without reason, but is actually a good (default) value.

Sections always need an IDService.

1. Check if an alias is present, so that the constructor creates one.
2. Only register the value IDs, when creating a valid element. Invalid 
elements generate and register IDs in the constructor (else path).

All page views were wrongly updated with the selected page instead of 
keeping the page index they were responsible for.

Should solve all issues with initializing Geometry elements.

#735

#738

#733

#725

This should avoid initialization issues with Geogebra elements, when 
placed on a hidden page.

#734

This avoids problem with the selected index when moving pages.

#737

Not closing the menu does not make sense when moving or deleting pages.
It was only useful to avoid closing when clicking on the menu without 
clicking a control. Losing this is acceptable.

Also disallow deletion of only non-permanent page.

#736

IDs can and will be generated by the element constructors.