Add 3 new REST API calls for audit log

Hi,

This is the bpm-console part of a new feature: to have a REST API in bpm-console to query already finished process/node/task instances.

Please review, and merge if it looks good. Once that's done, please also review https://github.com/droolsjbpm/jbpm/pull/43, which is a runtime (but not buildtime) depenency of this pull request.

Thanks,

Miklos