Finder as presenter

As part of the work to reduce Tech Debt in Finders, I decided that I should refactor how the Finder is displayed by sending the schema to the Content Store as part of the details hash and introducing a Presenter to simplify parsing the response. This allowed me to get rid of the Finder model (as that was basically all it was doing) along with it's horrible `Finder#get` method and a bunch of Parsers which we don't need now.

With this, I also refactored the Facets as we no longer need to parse hashes and build them into OpenStructs. Doing this, I discovered that there was lots of code still around that we don't need. Mostly from before we built the custom UI components so that was removed, along with the Radio Facet which we don't use anymore.

All this work has the added benefit of being able to remove the dependancy on Finder API for this project.

This is a **big** refactor, so it's best to leave merging this a couple of days so we can get everyone's opinions on this.
This is used here, a subset is used in the `email_alert_subscriptions_controllers_spec` (below) and could be used to build the OpenStruct used in facet_parser_spec.rb.

I still think we'd be better off with this in a fixture somewhere then altering the other tests; **however** this isn't something that will stop me merging this PR.