Event code update
Created by: apcarp
This branch updates code to better handle 'no prior data' event codes. These are used for the very first data point in a mya table and add informational metadata as to why there is no prior data (data purged, start of archiving, etc.). The UNDEFINED event code also got a new number indicating that it is a disconnect style event.
I did not update any documentation beyond the javadocs directly associated with changes I made.
Since this is a major release, the deprecated mySamplerFloatEventStream functionality was removed.