Add JSON endpoint for facia collection ID's

This add's and API endpoint for to request container HTML markup and array of trail data for a specific collection ID. This then allows us to use this as a data source to drive onward journey components.

#### Note
This currently uses a query-string to supply the path of the front it came from to circumnavigate a complex lookup for the collection. This will all go away with the work @janua is doing to refactor Facia. In the future we should just eb able to do: ```CollectionCache.get(id)```

@janua @gklopper As discussed can you please sanity check my Scala foo.

/cc @stephanfowler @commuterjoy this allows you to add your RSS endpoint.