Fix Doxygen configuration files' input file exclusion filters.

Fix up demo documentation device compatibility list to be as general as possible to reduce changes required as Atmel releases more devices within the same USB AVR series.

Make unfinished device mode applications use the VID/PID reserved for LUFA development devices.

Removed mostly useless "TestApp" demo, as it was mainly useful only for checking for sytax errors in the library.

MIDI device demos now receive MIDI events from the host and display note ON messages via the board LEDs.

Added beginnings of a MIDI class bootloader.