add animationTimeScale to scene. to control whole scene animation speed.

src/babylon.scene.ts

@@ -509,7 +509,10 @@
 
         private _animationRatio: number;
 
-        private _animationStartDate: number;
+        private _animationTimeLast: number;
+        private _animationTime: number = 0;
+        public animationTimeScale: number = 1;
+
         public _cachedMaterial: Material;
 
         private _renderId = 0;
@@ -1283,19 +1286,19 @@
                 return;
             }
 
-            if (!this._animationStartDate) {
+            // Getting time
+            var now = Tools.Now;
+            if (!this._animationTimeLast) {
                 if (this._pendingData.length > 0) {
                     return;
                 }
-
-                this._animationStartDate = Tools.Now;
+                this._animationTimeLast = now;
             }
-            // Getting time
-            var now = Tools.Now;
-            var delay = now - this._animationStartDate;
-
+            var deltaTime = (now - this._animationTimeLast) * this.animationTimeScale;
+            this._animationTime += deltaTime;
+            this._animationTimeLast = now;
             for (var index = 0; index < this._activeAnimatables.length; index++) {
-                this._activeAnimatables[index]._animate(delay);
+                this._activeAnimatables[index]._animate(this._animationTime);
             }
         }