#70 Multi-Button Mouse Support

[Dean]

First of all, prgm is amazing as is, and I would continue to use it
even if it were never updated again! Now, I'd really love to be able
to use mouse buttons 3, 4, etc. for switching between desktops.
Exposé is able to use these buttons, even for unsupported mice, so
it has to be possible. I can't really code a whole lot, but I'd be
happy to help out any way I can. Thanx!