Add polls (#10111)

* Add polls

Fix #1629

* Add tests

* Fixes

* Change API for creating polls

* Use name instead of content for votes

* Remove poll validation for remote polls

* Add polls to public pages

* When updating the poll, update options just in case they were changed

* Fix public pages showing both poll and other media

db/migrate/20190226003449_add_poll_id_to_statuses.rb

@@ -0,0 +1,5 @@
+class AddPollIdToStatuses < ActiveRecord::Migration[5.2]
+  def change
+    add_column :statuses, :poll_id, :bigint
+  end
+end