increased coherence of QoS policies (and more accurate commentary)
Adding some crude rules to regression test QoS policy profiles on the fly.  Will warn when QoS settings do not seem to make sense together in a previously discovered way.
decrease writer lifespan for observed data to 30 seconds.  This is a compromise for the lack of temporal sample constraint on the reader side.  This could be done other ways in the future.
Adds a loadingHistorical() call to WaveformSource and a crude message in the UI for when it returns true.  Still investigating performance implications of continuous calls to wait_for_historical_data
Catching this exception for now until something more robust can be done with it
"receiving" is a better descriptor for backfilling historical data than "retrieving"
new version 0.2.1
30 second lifespan meant to be applied only to observed data not as a default for all writers.
Promote to 0.2.2