Persistent Observer - allow to listen for event for all records of a model

Persistent Observer - allow to listen for event for all records of a model

- allow to listen for a event for all records of a given model (instead of
  just one specific record)
- change API, fire event takes an event now. So concrete implementation can
  pass additional information through the fired event

Change-Id: Ia1deb210f4a9bfe0d36965590a3465ed3f98c90e
Reviewed-on: http://gerrit.tine20.com/customers/4976
Tested-by: Jenkins CI (http://ci.tine20.com/)
Reviewed-by: Cornelius Weiss <c.weiss@metaways.de>