Adding first version of SuperLoader

This class is the Phaser loader as it should be: it comes with promises,
can be easily run out of the "preload" phase and won't crash if the
scene is destroyed before textures are loaded.

pusher/src/Model/PositionDispatcher.ts

@@ -92,8 +92,10 @@ export class PositionDispatcher {
 
     public removeViewport(socket: ExSocketInterface): void {
         // Also, let's stop listening on viewports
-        for (const zone of socket.listenedZones) {
-            this.stopListening(zone, socket);
+        if (socket.listenedZones) {
+            for (const zone of socket.listenedZones) {
+                this.stopListening(zone, socket);
+            }
         }
     }