Add support for starting and stopping a job queue

apps/job_processor/exceptions.py

@@ -1,14 +1,14 @@
-#class WorkerAlreadyDisabled(Exception):
-#    pass
-    
-    
-#class WorkerAlreadyEnabled(Exception):
-#    pass
-
-
 class JobQueuePushError(Exception):
     pass
 
 
 class JobQueueNoPendingJobs(Exception):
     pass
+
+
+class JobQueueAlreadyStarted(Exception):
+    pass
+
+
+class JobQueueAlreadyStopped(Exception):
+    pass