Added a UI theme option to the boot options menu.

Here's an initial implementation of changing the UI theme at run time. You really need to review this before merging it. It works fine. However, the design might be wrong or prone to bugs. Let me know what you think and I can go back and update some things to fix it.

The basic idea of the code is pretty straight forward. Three things needed to happen for this to work.

1.) I had to add an option in the boot menu and provide a way to query for the relevant information from the GUI manager. This part I think is in pretty good shape.

2.) The concept of the cursor was never stored in the engine. The initial value was just read in, set, and forgotten about. So, I added some code to store and changed the logic to set the cursor when it sets the rest of the UI theme. This should also be in decent shape.

3.) This is where things kind of start to get messy. With just 1.) and 2.), future UI's will work fine. You can load a game or do a battle and the UI will look correct. However, the current boot menu UI will not reflect the theme change. So, I hacked in some code to tear it all the way down and build it back it up.

Let me know what you think.

Have a good one.