Added a donut chart to the quota view

Moved morris.js out of the statistics plugin

src/static/charts/morris.css

@@ -0,0 +1,2 @@
+.morris-hover{position:absolute;z-index:1000}.morris-hover.morris-default-style{border-radius:10px;padding:6px;color:#666;background:rgba(255,255,255,0.8);border:solid 2px rgba(230,230,230,0.8);font-family:sans-serif;font-size:12px;text-align:center}.morris-hover.morris-default-style .morris-hover-row-label{font-weight:bold;margin:0.25em 0}
+.morris-hover.morris-default-style .morris-hover-point{white-space:nowrap;margin:0.1em 0}

src/static/pretixcontrol/js/ui/quota.js

@@ -0,0 +1,20 @@
+/*globals $, Morris, gettext*/
+$(function () {
+    if (!$("#quota-stats").length) {
+        return;
+    }
+
+    $(".chart").css("height", "250px");
+    new Morris.Donut({
+        element: 'quota_chart',
+        data: JSON.parse($("#quota-chart-data").html()),
+        resize: true,
+        colors: [
+            '#0044CC', // paid
+            '#0088CC', // pending
+            '#BD362F', // vouchers
+            '#F89406', // carts
+            '#51A351' // available
+        ]
+    });
+});

src/static/pretixcontrol/scss/main.scss

@@ -4,6 +4,7 @@ $fa-font-path: static("fontawesome/fonts");
 @import "../../fontawesome/scss/font-awesome.scss";
 @import "../../typeahead/typeahead.css";
 @import "../css/metisMenu.min.css";
+@import "../../charts/morris.css";
 @import "../../datetimepicker/_bootstrap-datetimepicker.scss";
 @import "_sb-admin-2.scss";
 @import "_forms.scss";