jdbc experiments, stage VI

ADDED
* ChatRoom entity + dao
* ChatUser entity + dao

REFACTORED
* id sequencer removed
* getIdFromSequencer added to AbstractDAO
jdbc experiments, stage VII + log4j

ADDED
* chat.users_rooms transfer table
* ChatRoomDaoImpl new methods
* ChatUserDaoImpl new methods
* custom EntityMapper
* Log4j integrated in commons component
Create README.md