This commit includes several pieces of functionality to enable services
to be removed and the page to present information that this has happened
but also keep the deleted information on the page. Along with the more
usual blocking query based listing.
To enable this:
1. Implements `meta` on the model (only available on collections in
ember)
2. Adds new `catchable` ComputedProperty alongside a `listen` helper for
working with specific errors that can be thrown from EventSources in an
ember-like way. Briefly, normal computed properties update when a
property changes, EventSources can additionally throw errors so we can
catch them and show different visuals based on that.
John Cowen