Checks datanucleus StoreManager for support of SchemaAwareStoreManager
before casting.

Now supports Neo4J embedded DB with DataNucleus.
ISIS-983 Enabled Embedded Neo4J support

Added datanucleus-neo4j in a neo4j pom profile [simpleapp, todoapp]
Added neo4j example setting in persistor.properties [simpleapp, todoapp]
Added .gitignore to ignore embedded neo4j generated testDB folder
[simpleapp, todoapp]
Merge remote-tracking branch 'jdbranham/master'
ISIS-983: testing neo4j support for todoapp and simpleapp.

changes:
- the todoapp has been changed to use a Set (rather than SortedSet) for ToDoItem#dependencies... would seem that DataNucleus' neo4j support returns an object of the incorrect type.
- the neo4j settings in persistor.properties has been moved to the end (and is commented out).
- replaced tabs for spaces in pom.xml.

With these change the webapps run ok:
* edit in neo4j setting in WEB-INF/persistor.properties
* build using "mvn clean install -P neo4j"
* run using "mvn antrun:run -Pself-host,neo4j -o"

However, note that the integration tests were tested and do NOT pass:
- the issue for simpleapp was that looks like unique index constraints are not implemented,
- the issue for todoapp looked down to ordering of the dependencies collection.

This commit also:
- renames ToDoSystemInitializer to ToDoAppSystemInitializer (for consistency with simpleapp)
- adds a new putDataNucleusProperty in IsisConfigurationForJdoIntegTests