- created VclVBox control which creates SlideTransitionPane
- SlideTransitionPane extended with second constructor
  which loads ui in horizontal mode
- introduced CloseMethod for NotebookBar to kill widgets in right order

Change-Id: Ic3ba35cb7734aa744a4804c5b670fed7c1bec204
Reviewed-on: https://gerrit.libreoffice.org/25844Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>