The new central CloneSdrObject in the case of SdrTableObj
has to do some more stuff due to the UNO API TableModel in-
volved and stuff. This is done in ::operator= now and thus
will work uniformly now (multi-select and copy).
At the same time there is functionality to clone/copy only
a partial Table in Draw/Impress when e.g some Cells are
selected. To reflect this code is needed to 'crop' the
just cloned SdrTableObj to the current selection. This again
was pretty hard due to side-effects in the implementation
using a mix of UNO API and SdrModel-stuff.

Change-Id: I9816e1caf34e29021d46d6dd9bb935c634f5ba2e
Reviewed-on: https://gerrit.libreoffice.org/53975Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>