When the WebDAV sync draft first came out the responses were each
contained in a DAV::sync-response tag, but by -03 this has changed
to a DAV::response tag since the format of the tag contents now
match this existing tag structure.
Unfortunately some client software in the wild depends on this
being a DAV::sync-response so the config option is needed to
interoperate with this software.
The sync-collection report was looking for $request->CollectionID()
but this is not set for bound collections and we have to use
DAVResource methods to retrieve it.
This is so we get dav_name correct for delete actions, which
will otherwise be null since there is no caldav_data or
calendar_item record for them any longer.
