New UI backdrop type added

I added a new backdrop type to Ardor3d's UI system yesterday that allows you to specify multiple images, each with their own placement, scaling, pivot points, rotations, etc. Combining this with a SpatialController allows for some interesting animation effects in the UI.

As a simple example of how this new backdrop can be used, you can check out the 3rd tab of the "SimpleUIExample" in ardor3d's example module. In there, I've used the following image to create a simple clock:



The UI system lets you dissect this image into smaller image portions and then act on each as an independent entity. Here it is in action, all contained within the backdrop of a simple UIPanel.



Nothing super fancy, but hopefully a good base for many interesting and useful custom UI widgets.