Clean up imports.
Throw exception if transaction is already open.
Close transaction on shutdown.

Might want another way to do this other than with commit()...left a todo: there.
Add feature checks for memory support on ExceptionConsistency tests.
Throw exception when trying to assign an id in neo4j to vertex.
Throw exception when trying to assign an id in neo4j to edge.
Throw exception if all property values are not valid when adding an edge.
Use tx.close() so that transaction shutdown behavior takes over on graph shutdown.
Removed parallel stream processing, for now.
All exception consistency tests work for neo4j.
Make sure that the "second" graph gets cleaned up on error.