FR: Allow scheduled snapshot creation

[claytonpeters]

No description provided.

[jakemalley]

@claytonpeters What's the use case for this? I was under the impression snapshots are something we try to use sparingly and keep as short lived as possible? (unless we also expire them automagically)

[claytonpeters]

@jakemalley It was a request from ops, because they quite often get requests for "can you snapshot all these machines at time x so we can do the upgrade at time 'y'?" which usually involves them logging in at home to do it.