Description of problem:

In BPMS 6.2, task events are fired when the status of a human task is changed, but not when the task contents is modified without changing the task status (e.g. by a call to UserTaskService.saveContent(Long, Map<String, Object>))

My customer has two use-cases for this:
* track all changes to task content in an audit trail.
* use task content events to duplicate task content data in a secondary data store (mongo, elasticsearch) to allow enhanced searching capabilities on task content data.