Multi providers 80421

This removes Surveyor specifics from the survey service. Now all surveys are generic UrlServices. Existing surveyor data will be migrated to the new approach. 

Here are some notable refactors:

* model subdirs are now autoloaded
* external service model classes are now under their own dir
* let(:authable) is now looked for by controller_spec_helper if @authable is not found
* external_service_receivers.response_data now stores a JSON String

Other codebase cleanups were made too.