Touching color implementation (#312)

* Touching color draft implementation

* New constant for CPU/GPU render split determined, removing query param

* Small fix for pick tests

test/integration/index.html

@@ -11,6 +11,7 @@
     <script>
         // These variables are going to be available in the "window global" intentionally.
         // Allows you easy access to debug with `vm.greenFlag()` etc.
+        window.devicePixelRatio = 1;
 
         var canvas = document.getElementById('test');
         var render = new ScratchRender(canvas);