Refactor Instrument#response_set to Instrument#response_sets #3034

### Summary

An instrument can have many response sets, yet there was code in `Instrument` for a `response_set` method that returned the first response set. I needed to find all the instances this method was being used, evaluate and change the behavior to handle multiple response sets or reference a single instance from the collection. Along the way, I pulled out some of the business logic from the controllers to the models.

##### Changes
* `ContactLinksController#setup_instrument_variables` populates instruments with reasonable defaults. Pull most of the logic out into the models. Refactored to accept multiple response sets. Refactored instances for the views
* `EventsController` Pull out the default setting logic into the model. Refactored the models to accept multiple response sets
* `Instrument` Deleted `#response_set` and `#response_set=`.  
* `Views` Adapted to multiple response sets.
* Solid chunks of testing.