Common reorg (#8025)

* Re-organize common folder

* fix: Correct paths in tests

* fix: move new content to proper folder

* chore: Move audio folder to assets

* Move sprites to sprites assets directory

* Move css sprites to assets directory

* Split out readmes for common code and sprites

* Move images to assets directory

* Move destinatin of shared browserified file

* remove unused file

* move compiled js to client-old

* Fix karma tests

* fix: Correct paths for sprites

website/common/script/libs/extendableBuiltin.js

@@ -0,0 +1,11 @@
+// Babel 6 doesn't support extending native class (Error, Array, ...)
+// This function makes it possible to extend native classes with the same results as Babel 5
+module.exports = function extendableBuiltin (klass) {
+  function ExtendableBuiltin () {
+    klass.apply(this, arguments);
+  }
+  ExtendableBuiltin.prototype = Object.create(klass.prototype);
+  Object.setPrototypeOf(ExtendableBuiltin, klass);
+
+  return ExtendableBuiltin;
+};