Adds processAllLocalObjectsForChanges to Simperium.

Objects that differ to their ghost and have no pending changes remain
stuck in a bad state until a local change occurs because any remote
diffs are transformed against the local diff, but the local diff
remains unsent. This method resolves the bad state by sending a
change for any objects which differ from their ghost. Its performance heavy
and therefore should only be called manually when needed.
Might as well do JSON string encoding off the main thread.
Add back in the obtain permanentID for children code.