Place requests for vault destruction in activity feed for administrators

[brainchild0]

Issue #416 explains how an administrator may process a request for destroying a vault.

However, the hidden location of the queue display makes it unlikely that an administrator naturally would find a newly queued item.

If the application could place a notification on the activity feed for administrators, then it is likely they would discover the request promptly.

As a further note, some administrators may prefer to allow users to elect to destroy vaults. If a vault is owned exclusively by a user, then it is unclear why the request must be approved.