Playground v4.4 : QRcode is back. Version selector too.

Playground/js/config_versions.js

@@ -0,0 +1,5 @@
+CONFIG_last_versions = [
+    ["4.0.3","https://unpkg.com/babylonjs@4.0.3/babylon.js"],
+    ["4.0.0","https://unpkg.com/babylonjs@4.0.0/babylon.js"],
+    ["3.0","https://unpkg.com/babylonjs@3.0.7/dist/preview%20release/babylon.js"]
+];