This reverts commit 6ddfd7f7.

This makes no sense in expert mode either but is harder to solve. :)

This would alles changing things that are deliberately left out in the 
props panel.

The background color is set via data-attribute so it can be turned off 
for the parent div but still used in the child (button).

For Table compatibility.

Not above.

- Remove superfluous width and height. This is already done by parent 
elements in player and editor.
- Remove superfluous div and use host element instead.

Dimensions are mandatory but with only height and width.

Also add controls to non-expert mode.

This change is for GeoGebra-Elements, which have mandatory width and 
height.