Added username auditing when possible.

Before, we were only auditing the user's username when the request succeeded. Now, we will attempt to audit the user's username any time it is available.

References #627
Updated the timestamp in audit/read calls.

The timestamp being returned was not in a valid ISO-8601 format. It now is.

Note: This appears to breaking the Admin utility in teh current front-end.

Closes #626
Merge branch 'ohmage-2.16' of github.com:ohmage/server