code: public ExtendedRelation addSimpleAttributesRelationship(
  			String baseTableName, SimpleAttributesTable simpleAttributesTable,
  			UserMappingTable userMappingTable) {
  		return addRelationship(baseTableName, simpleAttributesTable,
  				userMappingTable);
  	}
docs: Adds a simple attributes relationship between the base table and user
  simple attributes related table. Creates the user mapping table and
  simple attributes table if needed.
  
  @param baseTableName
  base table name
  @param simpleAttributesTable
  user simple attributes table
  @param userMappingTable
  user mapping table
  @return The relationship that was added