better dto metdata serialization test
Synchronize SystemTime.UtcNow better
Adding TemporalAsserted metadata

Provides much better tracking of the transaction-time dimension than
just looking at raven's last-modified-date metadata.
Using history document instead of revisions index

... for everything except activation.  The index is now just for pending
documents so the activator can run.
Use consistent naming
Removing GetTemporalRevisionsFor methods

They are redundant, now that we have GetTemporalHistoryFor
Set version to 2.0.6