Only groups within the facility should be visible when a coach logs into a particular facility

Fixes Issue #2446 
It's not good Backbone style to be passing extra parameters into the fetch method, so we should really be passing it in when initializing the Collection. But looking at how the rest of the JS in this file is organized, that would be tricky, so you can leave it like this for now. Could you add a comment at the top of the file:

`// NOTE: don't look here for good Backbone examples. Instead, look at the store app, or sidebar nav.`
`// TODO(jamalex): refactor the Backbone code in this file.`