More Tweaks

Making changes to GameObject and Scene classes, and the Install Pipeline.

The locatable flag is added to GameObject and determines whether the GO is loaded into the Locator on install. This allows for transient GOs that do not permanently register.

Some of the details of the Install Pipeline were removed, in particular the logic that triggered on Scene instances. There is now an explicit Scene Start method and event, so a Scene can be built up completely before displaying it. There is also now a SceneInstallSentinel GO you can use to "signal" when an install sequence on the Scene is complete.

The Locator was added to the LoadedCallback.loaded() signature, so now you can access other GOs from this callback.

The simplifications also put more emphasis on the Bind Target List; this is now the only way to populate composite components like Scene and GameObjectCollection, which no longer have accessible add() methods. One consequence of this is every GO must bind (at minimum) with the scene that contains it.

If you are using GameObjectCollection to group GOs, then that name must also be in the list.

This also opens up the ability to "self bind" so your GO can perform additional logic after loading completes, and affect other GOs via the supplied Locator.