Annotations: Text Editing for Annotation View works

Editing textual-based annotation entries in the table works now.
Also unintended cancel operations (e.g. when clicking onto another cell)
are catched and handled correctly.

It remains to make the implementation more genierc to be reusable for
other views.

Issue-Ref: 4014
Issue-Url: https://af3-developer.fortiss.org/issues/4014


Signed-off-by: Andreas Bayha <bayha@fortiss.org>