Refactor CompositeIdTest
OGM-182 Add StringDateTypeDescriptor and TimestampDateTypeDecriptor
OGM-182 Add EmptyAssociationSnapshot
OGM-182 Add test to check a PUT_NULL tuple operation
OGM-182 Add module for Neo4j
OGM-182 Enable Neo4j module
OGM-182 Document Neo4j data store provider