server: added BaseRestlet for proper status, method and error handling
server: send error on invalid params in NotificationRouter
server: ExecuteQueryRestlet extends BaseRestlet
server: DefaultRestlet extends BaseRestlet
restlet: more cleaning in DefaultRestlet
server: AccessObjectByIdRestlet extends BaseRestlet
server: BaseRestlet supports additional optional params
server: OdsRouter uses BaseRestlet
server: NominatimRouter uses BaseRestlet
server: return 204 on success with no content
test: fixed NotificationManagerTest
test: added ClientFactoryTest
test: added BaseRestletTest and RestletResultTest