Fix issue with login pages appearing inside the app (not properly redirecting)

Adds an auth filter that returns a special error code when a user's session has timed out and the call was an ajax call.
Adds a global ajax error handler to force a page refresh to initiate the proper redirection to login screen (maintaining the session info).
Merge branch 'master' of https://github.com/nla/banjo
Merge branch 'master' into bug/acm-dsc-581
Merge pull request #693 from nla/bug/acm-dsc-581

Fix issue with login pages appearing inside the app (not properly redirecting on session expiry)