feat(fonts): download fonts from grafana instead of CDN

Makes its possible to run grafana without internet access.
The performance hit by not using a cdn is very small since
most grafana instances are setup on locally.

closes #4223

tasks/options/concat.js

@@ -22,6 +22,11 @@ module.exports = function(config) {
       dest: '<%= genDir %>/css/grafana.light.min.css'
     },
 
+    cssFonts: {
+      src: [ '<%= genDir %>/css/fonts.css' ],
+      dest: '<%= genDir %>/css/fonts.min.css'
+    },
+
     js: {
       src: [
         '<%= genDir %>/vendor/npm/es5-shim/es5-shim.js',

tasks/options/sass.js

@@ -6,6 +6,7 @@ module.exports = function(config) {
       files: {
         "<%= genDir %>/css/grafana.dark.css": "<%= srcDir %>/sass/grafana.dark.scss",
         "<%= genDir %>/css/grafana.light.css": "<%= srcDir %>/sass/grafana.light.scss",
+        "<%= genDir %>/css/fonts.css": "<%= srcDir %>/sass/fonts.scss",
       }
     }
   };