Remove poll votation types

Unfortunately this feature wasn't properly reviewed and tested, and it
had many bugs, some of them critical and hard to fix, like validations
being skipped in concurrent requests.

So we're removing it before releasing version 1.1. We might add it back
in the future if we manage to solve the critical issues.

This commit reverts commit 836f9ba7.

config/routes/poll.rb

@@ -5,12 +5,6 @@ resources :polls, only: [:show, :index] do
   end
 
   resources :questions, controller: "polls/questions", shallow: true do
-    member do
-      post :answer
-      post :prioritized_answers
-      delete :answer, to: "polls/answers#delete"
-      post :create_answer, to: "polls/answers#create"
-      get :load_answers
-    end
+    post :answer, on: :member
   end
 end