Snapshot 'Age'

Hi Will,

For #2, on the latest version of that datasource there is a field for snapshot_age_hours, which, by default doesn't have an alert threshold but if applied could alert if a particular snapshot is over a certain age.  #1 is a bit more tricky since it would require an aggregate measure across multiple instances.  It could be done with a scripted datasource but but the good news is we are working on an upcoming feature that will be a much better way to solve this.  More to come when we are ready to release.

~Forrest