増加Task和Timer机制

Task使用方法：
public SomeTask : Task
{
	protected override void onUpdate ()
	{
		// do something here...
	}

	protected override void onStart ()
	{
		// do something here...
	}

	protected override void onStop()
	{
		// do something here...
	}
}

public OtherClassMethod()
{
	SomeTask task = new SomeTask();
	task.start();
}

Timer使用方法：
public OtherClassMethod()
{
	KBEngineApp.app.addTimer( 0.5f, 0.1f, this.OtherClassMethodCallback, "I am come back" );
}

public OtherClassMethodCallback( Int32 timerID, object userdata )
{
	// do something here...
}