Expand subscriptions to notify on status and condition changes

[#1]

Subscriptions are helpful, but currently only capture a portion of what is going on with the task or issue. Status and condition changes represent a core part of the item's progress and it would be very helpful keep folks apprised of what is going on by having subscriptions push out a notification if the item's status or condition changes.

In our organization we often have people interested when and issue closes or just generally where an issue is in the a workflow. Having subscriptions keep them updated would be great.

Thanks.

[#2]

This desperately needs to be changed - we have so many team members that need to be updated on status changes/when a document is uploaded etc, but the only people who can receive these notifications are assignees and the one primary contact. There should also be a way to add subscribed users when submitting an issue through a request queue (or ability to add multiple Primary Contact). Currently, users can only be subscribed after an issue is submitted, which often just doesnt happen.