Add a constructor argument to salobj Controller and BaseCsc that allows commands to be missing (but still requires that any existing do_x methods have corresponding cmd_ topics). Other commands should raise salobjExpectedError with a message "not implemented". This will make it much easier to write minimal mock controllers, since they only have to implement the few commands they actually mock.
Update ts_atdometrajectory and ts_mtdometrajectory to use these. Look at ts_mtmount and ts_mtrotator as well.