instructions about enabling Gearman
Merge branch 'master' into jobs_daemon_ui_create_new_dump
don't show the "create new dump" button if Gearman is disabled
wrappers around Gearman's "enqueue_on_gearman()" and "run()" to log the enqueued / running / finished / failed jobs in the PostgreSQL database (because Gearman itself doesn't provide that facility)