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/_big_statistic.haml

@@ -0,0 +1,13 @@
+- reverse ||= false
+- variant = variant_from_delta(delta, reverse: reverse)
+.dashbox.text-center
+  %span.fa
+    = fa_icon(icon)
+    = value
+  %p.text-nowrap
+    %small
+      = subtitle.pluralize(value)
+      %span.label{ class: "label-#{variant}" }
+        = delta
+        since you last logged in
+

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

app/views/application/_line_chart.html.haml

@@ -0,0 +1,15 @@
+:ruby
+  options = {
+    legend:   'bottom',
+    download: true,
+    messages: { empty: 'No data' }
+  }
+
+.row
+  .col-md-12
+    .text-center
+      %h4
+        = title
+.row
+  .col-md-12
+    = line_chart data, options