This allows for persistent database connections for workers.

Don't override LVALERT_OVERSEER_INSTANCE settings from
envrionment variables.

1) Fixed a 500 Internal Server error when removing labels from events
   that do not exist. Basically the ValueError.message method was
   depreciated in python3; replaced it with a str(error).
2) Bumped version to 2.8.0

Fixed LVAlert server for "test" container, and fixed 500 server error
when sorting p_astro list for the public event page. I think this

https://stackoverflow.com/questions/27776026/lambda-arguments-unpack-error

fixes it.

Update base.py: updating the version number to "2.7.1-1". There's no functional differences, just a few settings for the new AWS deployment. I'm also adding the "*-1" qualifier so that I and users can tell that the new AWS deployment is in place and working. 

* Switch from VOEventLib to voevent-parse due to significant
  string-bytes issues in VOEventLib
* Remove bad exception handling in events API for creating a
  VOEvent
* Add parameter checking to events API for creating a VOEvent
* Combine VOEvent building code for events and superevents into
  a single instance which handles both cases

This is not needed anymore with the changes to the group infrastructure
which add an optional 'ldap_name' to groups whose membership should be
managed by LDAP queries and shib sessions.

ligoauth.models.AuthGroup is an enhanced version of the builtin Django
Group model. We add useful attributes like a description, ldap_name,
and Tag.  These can be used to abstract things that are presently
handled manually, like inheriting membership from an LDAP group or
allowing access to view log messages/files with a specific Tag.

I ran some tests comparing this multi-table inheritance setup to
adding a OneToOneField and loading it with/without select_related.
After 1K trials, the DB query times looked comparable and didn't
require multiple queries for this arrangement, so the convenience
seems to be worth it.

The commit creates the model and populates an instance for existing
each existing Django Group.

When applied, this makes a view publicly available *if* the
settings.UNAUTHENTICATED_ACCESS switch is True; otherwise you
must be authenticated. This will be useful to propagate to
most other views to make this settings switch globally effective
at some point.

Move some unused/non-functional menu items to live under a new
"Other" item: create (event), reports, and RSS.