Added support for UNDO/REDO for changes in Diagram ModelData.
This is currenly applied/used in the DiagramDialog for it's
Add/Remove actions (also supports Cancel of that dialog 1st
time ever). But it is defined more general to add/support
manipulating actions like clone/change_text etc. Also the
UI/dialog at he end will not be/stay modal, so this is a
test implemenation how to use it.
It uses an extract/apply mechanism to get/set the Diagram
ModelData at/for the UNDO action. That may be expanded as
needed for additional data in he future. It may also be
considered to modify the Connection/Point ModelData to
shared_ptr internally completely to avoid copying these
at all. OTOH it is not that much data to handle at all.
Change-Id: I4702ed908b79a476177fe66c0e3284898c6adda5
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/134118
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com>
1e01692076