Use chartkick globally

* Clean up legacy charting imports
* Update existing donut and line charts
* Create helpers for parsing out existing chart data
* Move chart partials to a more common path

app/views/application/_donut_chart.haml

@@ -0,0 +1,16 @@
+:ruby
+  combined_data ||= {}
+  data ||= chart_values(combined_data)
+  colors ||= chart_colors(combined_data)
+
+  options = {
+    donut:    true,
+    legend:   'bottom',
+    download: true,
+    messages: { empty: 'No data' }
+  }
+  options[:colors] = colors if colors.present?
+
+.text-center
+  %h4= title
+  = pie_chart data, options