Email alerts seem to be more problematic due to AWS SES rate
limiting and phone alerts are more important, so we should send
phone alerts first.

Addition to 058fd28d.

Discovered that AJAX requests to the API from the web view were
using certificates in people's browsers even if they were logged
out of the Django session.  So when they wanted to view the page
as a public user they still saw some extra information.

No security risk since they needed to have a valid certificate
anyway, but a bit annoying.

We've had some bad cases where a log entry is created, but the
file is not saved due to filesystem errors. So we put the file
creation in a try-except block and if it fails, delete the log
message that was just created before re-raising the exception.

Previous arrangement was not including zero-valued fields. We now
include all non-None fields.

Due to the fact that we are using multiple attribute authorities,
there are some cases (specifically email) where there are multiple
values provides for an attribute, separated by a semi-colon.

This update handles those instances and takes the first value in
the list.

Instead of looping over EmailMessage.send() calls, we now get the
email backend and send a list of messages. Note that the backend
sends the messages individually still but this cuts out some of the
overhead.

Prevents server errors from being generated when the filename is
"bad" and when the user specifies a non-integer version. This is
for superevent files; event files are handled separately, although
this should be unified at some point.

We use get_or_create now to add labels to a superevent in order
to prevent IntegrityErrors when a user makes the same request
too rapidly and both sneak by the initial check.

Not feasible to use multiple DBs for read or write operations at
present. We're going to have to revisit this at some point. We leave
most of the code in place but commented out.

Add capability for passing kwargs to AlertIssuer classes'
issue_alerts() method.  We take advantage of this in the update
alerts for checking for FAR changes and NSCAND state changes.