* Support link and group objects
* Support view sync by implementing view provider API getMDIView()
* Use handleChangedPropertyType() for object migration instead of
reimplementing Restore() because of a lots of changes in
PropertyContainer::Restore().
* Various other small fixes.
- when restoring DVD/DVA from old files, convert Source from
PropertyLinkGlobal to PropertyLink with Scope = Global. Note
subtle difference from Restore method in DrawView - PropertyLink
vs PropertyLinkList.
