Enabling audit event logging for authentication events.

This pull request needs to wait until the following is merged to undertow due to dependent changes: -

https://github.com/undertow-io/undertow/pull/57

The AS portion of the integration will also be dependent on this commit due to an API change: -

https://github.com/darranl/jboss-as/commit/818bb5424516f9cea6076daf5ae8bfb376800b9c