Add a high-res SNES skin, and fix digital axis detection

This should address issues where mapping a D-pad wouldn't work, when the D-pad shows up as an axis in the operating system. If you've encountered this issue, click "remap" on the menu to try again with the fixed version.

First self-contained package

This will let users run without having to hunt for Python and other dependencies, by simply running the included padpyght.exe.