Use buttons to destroy drafts and questions

As mentioned in commits 5311daadf and bb958daf0, using links combined
with JavaScript to generate POST (or, in this case, DELETE) requests to
the server has a few issues.

config/routes/admin.rb

@@ -346,3 +346,7 @@ end
 resolve "Poll::Question::Answer::Video" do |video, options|
   [:answer, :video, options.merge(answer_id: video.answer, id: video)]
 end
+
+resolve "Legislation::DraftVersion" do |version, options|
+  [version.process, :draft_version, options.merge(id: version)]
+end