Refactor/dry specialist document views

DRY up the views for specialist-document views so we no longer need to change multiple places when adding new doc types. 

One thing I dislike about this work is the use of 'controller_name' passed to the specialist_documents_path helper and the new_specialist_document_path helper from the views. In this case it will work fine as we should always be calling these helpers from the view in which case controller name will always be correct although I wonder if there is a better way. I am open to suggestions!