Draft: This is not a fix, it breaks rotation centers

There's some funky weirdness happening in getCenter. Not only does it cause complex documents with many iterating sp-use links to freeze, it also seems to be requiring a document update which isn't needed for other parts of the code, for example the resize handles seems to know where the object is and thus it should be possible to get the center of that box without such a large update.

Although finding out why child links need to be updated in order for a parent to know how big itself is, is an overly broad update error.