For now, it works for the Toolbar and the Context Menu tabs.
Normal top-level menus cannot be reset individually at the moment
because they are sharing a single xml file, and the removeSettings()
mathod doesn't provide per-item removal from within a single file.

Change-Id: I42d62dc26130e4c03cf75a1ce6dc9ff367a58d47
Reviewed-on: https://gerrit.libreoffice.org/41367Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>