cli_tag, non-functional form drop-down, show tags on event detail page.

Changed display of all date/time data to be UTC.
GPS times display UTC times when cursor hovers over them.

Required getting data out of ligolw tables.
Incidentally added processing of Omega results.

Added info for signing up to list on home page.

New model, EventLog.
Altered event "view" view and event_detail template to show log messages.

Changed uid to graceid, since it's not a uid.
Requires database change:
    ALTER TABLE gracedb_event DROP INDEX uid