This is done according to the Angular best practices and minimizes
namespace collisions when using other packages which might use the same
selectors.

Technically the selectors are not even becessary since we use an Angular
component factory to create element components but it is still useful
for the DOM element naming, for debugging purposes for example.

and DropListSimpleElement

This way the placeholder is exactly as big as the font size. There is no 
space for a padding here, as the normal dropList has.

Cloze elements are displayed inline and have no way to show a label.

Now manages height and width by itself. So no overlay div is needed in 
the cloze component.

Now only sends a list with IDs as value. The actual list manipulation is 
done with Material helper functions (transferArrayItem...).

Now correctly used the value of the dropped element.

It is meant to be used as inline positioned (sub) element. Therefore it 
has not postioning information and less property options than the normal 
drop list. Similar to the simple text field.