OGM-605 Add minor fixes to javadoc and comments
OGM-605 Fix import order in MongoDBAssociationRowFactory
OGM-605 Rename private methods in MongoDBAssociationRowFactory

  unprefix -> removePrefix
OGM-606 Rename test in OneToOneTest
OGM-606 Add JPA mapping example to MongoDB documentation
OGM-606 Neo4j images used in the documentation
OGM-606 Add JPA mapping example to Neo4j documentation
OGM-606 Add JPA mapping examples to CouchDB documentation
OGM-606 Add unidirectional many-to-many test
OGM-606 Add double field to BuiltInTypeTest
OGM-606 Add JPA mapping examples to Infinispan documentation
OGM-606 Add JPA mapping examples to EhCache documentation
OGM-606 Add testcase for enum types
OGM-606 Apply review remarks
OGM-606 Add note for null values