CRM-12277 Add info to Batch status change message to let users now that ...

...notifications will be sent for Pending Pay Later to Attended or Registered updates.

----------------------------------------
* CRM-12277: Notify batch Change Participant Status users that changing status FROM Pay Later TO Attended or Registered triggers email notification and payment status update
  http://issues.civicrm.org/jira/browse/CRM-12277