Input: byd - enable absolute mode

The Windows driver's settings dialog contains a visualization of the
regions for the hardware edge scrolling capability, which uses a
temporarily-enabled limited-resolution absolute mode.

This patch enables this during normal operation, and combines the
absolute packets with the existing relative packets to provide
accurate absolute position and touch reporting.

It also adds documentation for all known gesture packets and
initialization commands.

Reviewed-by: Chris Diamand <chris@diamand.org>
Signed-off-by: Richard Pospesel <pospeselr@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>