setup: Start a list of known gamepads.

Detect certain gamepads by name and automatically configure defaults
for buttons and axes, to minimize setup time. Supported so far are
the PS3 controller and AIRFLO gamepad.
setup: Fix disabling of joystick button bindings.

When setting a joystick button binding to -1 to disable it, set it
directly; do not go through to the physical button mapping layer.

Also add a quick note to encourage users to send in details of their
gamepads.
setup: Add configuration for Wii remote.

The Wii remote is not a HID device, meaning it cannot be supported in
a proper cross-platform way. However, it can be supported for
individual platforms. Add a fingerprint and configuration for a Wii
remote under OS X using the WJoy tool.