Exporting responses via CSV will now name the file based on the campaign name.

Closes #343
Removed a duplicate preference.

The 2.11 to 2.12 upgrade added two keys that were, again, attempted to be added in the 2.12 to 2.13 update script. This addition to the 2.13 update script has been removed.

References #457
Added XML exporting for observers.

observer/read/xml has the same parameters as observer/read, except that it requires that an ID and version be given, which will result in either 0 or 1 results. If it is 0, then a 404 is returned. If it is 1, then the body of the response is the XML.

Closes #481
Added the request ID to the audit log.

Requests are given an unique identifier for the log. That is now reflected in the audit log.

Closes #483
Fixed a bug when a user's token was not being deleted.

The token was being deleted on the server, and a cookie was being returned to delete it on the browser. However, a second cookie was being returned to the browser which did not have an expiration, therefore the token was being re-saved the browser.
Merge branch 'master' of github.com:cens/ohmageServer into ohmage-2.15
Readded the check for duplicate survey item IDs.

No two items, even across different surveys, may have the same ID.

Closes #513
Added a limit of 10 days to mobility/aggregate/read

The maximum duration for which a user is allowed to ask for data is now limited to 10 days.

Closes #523