Added migrations for gdb_pe robot cert and 'background' tag. Also added 'background' to the list of blessed tags in the settings module.

Fixed handle_uploaded_data to check whether the likelihood column is inf. Replaces 'inf' with the largest value that can be accepted by the mysql database. Fixes issue 1171. But we might find ourselves needing to check other columns in the future.

Fix for Issue #975, 'Versioned files displaying only newest versions in event detail page'. To fix this, we add a file_version field to the event log. This is accessed from the VersionedFile object at the time of file-saving. That way, the correct version can always be associated with any given log message.

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.

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

Create an EventLog if it does not.

How was this ever even working?