OGM-529 Add new test classes to check the mapping in Neo4j

  This commit decouple the tests so that a change
  will affect only the scenario involved.
OGM-529 Create sequences at startup
OGM-529 Label sequence nodes as SEQUENCE
OGM-529 Use proper cache implementation for sequence queries
OGM-529 Clean up, remove unecessary constants
OGM-368 Update Neo4j mapping tests for bidirectional relationships
OGM-368 Update expected number of associations in ManyToManyTest
OGM-368 Use only one relationship for bidirectional associations