Made changes to bring VOEvent closer in-line with what Mina and Peter are proposing. However, I still don't have their AlertVersion property. Nor do I have any of the analysis specific stuff, like ChripMass, frequency, etc.

Added basic 500 template. I did this because sometimes Django gives uninformative error messages (while in DEBUG mode) if the 500 template is absent.

analyst_comments and data_quality tags are blessed,
 but were not in the fixture for tags.

gracedb search GRB --columns=created
ERROR: 'unicode' object has no attribute 'isoformat'

Bug introduced in commit 3b31d9d3
    changed created time in eventToDict to UTC

https://bugs.ligo.org/redmine/issues/974

Caused neighbors section to go missing.

Models referenced non-existent fields in Django User model.
(fields which used to reference an obsoleted LIGO User model.