Move poll shifts form partial to a component

Thanks to it, we can move a few helper methods to the component.

app/assets/javascripts/admin/poll/shifts/form.js

@@ -0,0 +1,20 @@
+(function() {
+  "use strict";
+  App.AdminPollShiftsForm = {
+    initialize: function() {
+      $("select[class='js-poll-shifts']").on({
+        change: function() {
+          switch ($(this).val()) {
+          case "vote_collection":
+            $("select[class='js-shift-vote-collection-dates']").show();
+            $("select[class='js-shift-recount-scrutiny-dates']").hide();
+            break;
+          case "recount_scrutiny":
+            $("select[class='js-shift-recount-scrutiny-dates']").show();
+            $("select[class='js-shift-vote-collection-dates']").hide();
+          }
+        }
+      });
+    }
+  };
+}).call(this);