Add another mechanism to wait for replication to finish - uses polling, more like iOS test.
add testGoOffline() to check status after going offline.
implement goOffline(), testGoOffline() now passes.
Update status whenever notifying change listeners
Add restart() method
Move ChangeTrackerTest to replicator package.  Add docIds property, unused.
Refactor ChangeTracker to be in the replicator package
add testChangeTrackerWithDocsIds() and modify impl so test passes.
Propagate docIds from replication -> change tracker