(css) Update grunt-sass to v3.0

This release requires Node.js 8 or later.

UI/WebServerResources/Gruntfile.js

@@ -21,6 +21,7 @@ module.exports = function(grunt) {
     'js/vendor/FileSaver.min.js': ['node_modules/file-saver/dist/FileSaver.js']
   };
 
+  const sass = require('node-sass');
   require('time-grunt')(grunt);
 
   // Tasks
@@ -28,6 +29,7 @@ module.exports = function(grunt) {
     pkg: grunt.file.readJSON('package.json'),
     sass: {
       options: {
+        implementation: sass,
         sourceMap: true,
         outFile: 'css/styles.css',
         noCache: true,

UI/WebServerResources/package.json

@@ -27,8 +27,9 @@
     "grunt-contrib-watch": ">=0.5.3",
     "grunt-ng-annotate": ">=0.10.0",
     "grunt-postcss": ">=0.6.0",
-    "grunt-sass": "^2.0.0",
+    "grunt-sass": "^3.0.0",
     "kss": ">=2.1.0",
+    "node-sass": "^4.12.0",
     "time-grunt": "latest"
   },
   "browserslist": [