use new send-jobs-to-dvla task instead of send-files-to-dvla

the tasks (on the ftp app) do the same thing, but to improve clarity
i've renamed it to jobs, because we'll be adding a notifications one
soon

app/config.py

@@ -48,7 +48,8 @@ class QueueNames(object):
 
 
 class TaskNames(object):
-    DVLA_FILES = 'send-files-to-dvla'
+    DVLA_JOBS = 'send-jobs-to-dvla'
+    DVLA_NOTIFICATIONS = 'send-notifications-to-dvla'
 
 
 class Config(object):
@@ -226,7 +227,7 @@ class Config(object):
         },
         'run-letter-jobs': {
             'task': 'run-letter-jobs',
-            'schedule': crontab(minute=30, hour=17),
+            'schedule': crontab(hour=17, minute=30),
             'options': {'queue': QueueNames.PERIODIC}
         }
     }