Move databinding package from base.ui to kernel.ui

* Retain almost all ratings ratings
* Exception: AbstractTextCellDatabindingEditingSupport, whose
  setupFieldAssist() method was removed since
   * it would have introduced a dependency to another package in
     base.ui only because is "FieldAssist" class was referenced in
     the method *comment*.
   * However, this method is only used very rarely and users of the
     class setup up their field assist in createCellEditor() instead.

Issue-Ref: 3582
Issue-Url: https://af3-developer.fortiss.org/issues/3582



Signed-off-by: Simon Barner <barner@fortiss.org>