FEATURE: Poll breakdown 2.0 (#10345)

The poll breakdown modal replaces the grouped pie charts feature.

Includes:

* MODAL: Untangle `onSelectPanel`
Previously modal-tab component would call on click the onSelectPanel callback with itself (modal-tab) as `this` which severely limited its usefulness. Now showModal binds the callback to its controller.

"The PR includes a fix/change to d-modal (b7f6ec6) that hasn't been extracted to a separate PR because it's not currently possible to test a change like this in abstract, i.e. with dynamically created controllers/components in tests. The percentage/count toggle test for the poll breakdown feature is essentially a test for that d-modal modification."

lib/tasks/javascript.rake

@@ -69,6 +69,9 @@ task 'javascript:update' do
     }, {
       source: 'chart.js/dist/Chart.min.js',
       public: true
+    }, {
+      source: 'chartjs-plugin-datalabels/dist/chartjs-plugin-datalabels.min.js',
+      public: true
     }, {
       source: 'magnific-popup/dist/jquery.magnific-popup.min.js',
       public: true