Additional Rules integration.

We have:
* events fire for both object and datastream ingest, modification and purge
* the ability to set some properties on datastream and object including
    * object:
        * owner
        * state
        * label
        * models
    * datastream:
        * label
        * state
        * mimetype
        * content

There is also some additional conditions and action for dealing with datastreams, but especially those containing XML.