Shortcuts modules were added for the events and superevents apps.
Currently, they just contain 'is_event()' and 'is_superevent()'
methods.

Instantiating a new alerts app and moving the alert functionality from
events/alert.py to alerts/old_alert.py. This commit forms a starting
point where the old alert functionality is still in place and we can
rework the alert infrastructure to be more modularized, flexible,
and adapted to superevents.

handle changes to writeLog client function and clean up display name handling for tagging of event logs

changing format for event EMObservations and EMFootprint creation timestamps when these objects are converted to dicts

Adding custom pagination to superevents API to match events. It's bad, but will have to serve until we can redo the whole thing

updating event tag and event log tag resources to include more information than just a link to the detail page

adding superevent API urls - currently nesting them within the events API; should eventually be moved to a separate API app

generalizing and abstracting several models in the events app, as well as fixing many field parameters

Need to make sure values are actually numeric types before
just passing them to isnan(), since it can't handle them, apparently.

Adding some requirements to migrations to enforce proper ordering.

Renaming LIB -> oLIB and gstlal-spiir -> spiir, at the request of
the pipelines.

gstlal wants to set eff_distance to nan when they don't have a
meaningful value for it.  Unfortunately, we can't save that in the
database because MySQL numeric types can't deal with nans. So we
check for nans in this field and set it to NULL if it is nan,
before saving it in the database.

Updated from Django 1.11.5 to Django 1.11.14. Updated 3rd party
packages so that all of them have version requirements in
requirements.txt.  Also updated most of these packages to use the
newest versions.  A specific update to the twilio package required
some changes for how we determine the 'from' phone number. Also
alphabetized the packages in this file.  Finally, added the very
useful django-silk debugger/profiler.

Updated event static file serving to use X-Sendfile with Apache.
This is faster, more efficient, and seems to resolve the issue
with FITS file downloads from the web browser:
https://bugs.ligo.org/redmine/issues/6194

Added requirement that event.search is not None before checking
that event.search.name is MDC.  Fixes a bug which occurred when a user
tried to get an event by specifying 'M1234' when the event was not
an MDC event (and didn't have a search associated with it).

Missed one case where 'tag' should have been 'tags' in
58efeab3. Also updated same thing
in documentation.