Save and load xml:id as well as text:id and draw:id where necessary

ODF 1.2 migrates from draw:id and text:id to xml:id in most cases. This
patch introduces a new class, KoElementReference, that makes handling
id's mostly transparent.

It also changes KoShapeSavingContext to manage references and id's in
a transparent manner when saving. Most filters, even those that are
currently useless, have also been updated.

BUG:288644
REVIEW: 104074