Add django-user-sessions package for more easily managing sessions
and correlating them with user accounts.

We now have a single API endpoint, /api/, which can handle all
authentication methods directed to it.  The /apibasic/ and
/apiweb/ URLs will probably be maintained for legacy reasons,
but will not include any additional logic (they will just be
carbon-copies of /api/ under a different namespace).

We use a few redirects to handle login and extraction of the
shibboleth attributes in a post-login page.

Can be used to restrict access to a view to only the groups
whose names are passed as arguments to the decorator.

No need to have explicit view functions for a few basic views,
we just use the built-in TemplateView instead.

silk was slowing things quite a bit so we won't use it by default,
even in development instances.

Moved events.api and superevents.api into the new api app.
We want to have a versioned API, so these are now in
api.v1.events and api.v1.superevents, respectively. Part of this
change is that we require a custom reverse function (api_reverse)
for handling versioning. Much of the required code changes for this
migration include converting reverses to use this function and
changing relative imports appropriately.

New /latest/ page includes events and superevents. We also
move the old events 'latest' page to /events/latest/, changed the
view name, and fixed reverses to that page appropriately.

Modified events.view_utils.reverse to return an absolute url using
core.urls.build_absolute_uri.  This is helpful for when we issue
alerts without a request object available to construct the absolute
url.  Also updated the corresponding *toDict methods so as to
take advantage of this.

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.

This reverts commit f85b7c70.

Changes to improve speed of searches:
- remove neighbors from search by default
- select related objects for queryset in flexigrid response

on top.  Documentation is still very much under construction.

Added context processor for login URL, added login URL to base template, added embedded discovery service page.

Fixed problem with SPInfo and SPPrivacy URLS. Also changed name of /events/ view to 'home-events' so the 'home' view will point to the one that is actually public.

Removed 'Alpha' from the GraceDB homepage. Also added service provider privacy and info pages, which are required for federation with InCommon.

Added some features to gstlalcbc_report (semi-adaptive mass bins, default query, end_time template filter). Also refactored gstlalcbc_report into reports.py. Some other cleaning up.

To accomodate the fact that our Apache can't do Shibboleth *and* X.509
auth on the same URL and we want both kinds of auth available for the API.