Add hooks in client for updates

[dylwhich]

Right now the only way to get updates as they come in is to catch all of them and sift through yourself. This could be made much easier, by binding listeners for changes of the following types:

• For a single property of an object
• For any property of an object
• For a single property of any instance of a class
• For any property of any instance of a class
• For when an instance of an object is created/destroyed

[alexander-bauer]

This could use a JQuery-like 'event' system, where you bind callbacks by invoking client.$ClientRequestUpdater.onUpdate("Player", callback), or something of that nature.