Adding expire option for stashes on clients and checks

The stashes page lists the expire times for stashes.  The modal boxes have boxes to set the expire for either silence check or silence client.
It's ugly, but it's functional.  I'm not quite sure how to get the formatting pretty, but I'm definitely open to suggestions.
I'm not quite sure what to do with the "Silence checked clients" and "Silence checked checks" functionality, other than use the default expire values for each.  The defaults are set in the models.