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

spec/factories/users.rb

@@ -31,6 +31,7 @@ FactoryBot.define do
       Quisque cursus facilisis consequat. Etiam volutpat ligula turpis, at
       gravida.
     EOS
+    last_sign_in_at { Date.today }
     is_disabled { false }
 
     after(:create) do |user|