KerberosFilter should accept config for static pages and images to return incase of errors

[harshach]

We should've a config in KerberosFilter to remove auth for URLs. This will be helpful to display static pages in case of errors when the user is not authenticated. We should provide pattern match config option to match 1 or more URLs

[priyank5485]

https://github.com/hortonworks/registry/pull/247

Instead of adding it as a configuration, I felt its better if the application itself handles a 401 error redirection. However, the redirected static pages also go through the same filter since we register it for all dispatcher types and not just CLIENT. For that reason and otherwise i think its useful to have an "allowed.resources" property in the filter to bypass some of the static reources