Create and process external MDC events to test RAVEN pipeline; fixes #401 and #403

These changes create and upload external MDC events in order to regularly test the fully RAVEN pipeline. This is designed to create an external MDC event for every 2 MDC superevents, resetting every day. These joint coincidences should be able to be found by ligo-raven>=2.0 by including search='MDC' in ligo.raven.search.search().

The MR includes changes to:

• create MDC external events via first2years_external.py
• use se_search field for superevent searches with new release of ligo-raven
• update superevent with coinc FAR values when better coincidence is available

gwcelery/tasks/first2years_external.py

@@ -12,7 +12,7 @@ from . import lvalert
 
 
 def create_grb_event(gpstime):
- 
+
     new_TrigID = 123400000 + int(np.random.random() * 100000)
     new_date = str(Time(gpstime, format='gps', scale='utc').isot)