Checks datanucleus StoreManager for support of SchemaAwareStoreManager

ISIS-983
Added a check to datanucleus StoreManager for support of SchemaAwareStoreManager before casting.

This allows support for Neo4J embedded DB with DataNucleus.

The only relevant file is DataNucleusApplicationComponents.java
The others are configurations to run the SimpleApp with a Neo4J datastore by default.