Tag PropertyGraph v0.1.0

This version contains support for the tracking of changes to vertices and edges which is needed to support persistence logic (persisting changes to database or other store).  This version contains extensions that make it possible to load portions of a graph on demand (although the specific implementation for any specific store must be provided externally to this package). 

This version also includes new query operations that can be used to repeat sections of a query until some condition is met (such as when beginning with a set of vertices..following edges that meet some condition to new vertices... then repeating the previous steps until some larger network of vertices is selected..)..