- The Sandbox now deletes the Scene when the module is destroyed.
- Added the "ToyAssets" module as a dependency of the Sandbox.  This will stop it from being loaded/unloaded when switching between toys that use it.
- Set the assets to ignore the auto-unload by default.  This favours performance by removing asset unloads over memory usage.
- Purge the assets prior to a new toy loadsing to removing any idle assets from any previously loaded toy.
- The asset manager now tracks overall reference counts.  The SceneWindow now reports this in the metrics overlay.
- State reset for the particle-system to ensure that animation asset references are freed when the particle is released. The AnimationController needs some further work so completely remove the need to assign an animation-asset to it; rather it should use one assigned from the parent-owner object.  This is the typical use-case as an AnimationController would never be used on its own.  This would stop the doubling-up of animation of asset references.