Renamed SdrPage::Clone -> SdrPage::CloneSdrPage
Renamed SdrObject::Clone -> SdrObject::CloneSdrObject

Giving SdrModel is no longer an option, but a must (as
reference). This makes future changes more safe by force
usage to think about it. Also equals the constructors
which already require a target SdrModel.
Done the same for ::CloneSdrPage.

Change-Id: I06f0129e15140bd8693db27a445037d7e2f7f652
Reviewed-on: https://gerrit.libreoffice.org/53933Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>