Split out common defines/types from class drivers into a seperate common class driver directory.

Make central USB Class driver dispatch headers, used for both device and host modes.

Commit of new class abstraction APIs for all device demos other than the MIDI demo - not documented yet.

Removed scheduler and memory allocation libraries.

Added new EVENT_USB_StartOfFrame event in the library to indicate the start of each USB frame (when generated).

Removed Tx interrupt from the USBtoSerial demo; now sends characters via polling to ensure more time for the Rx interrupt.

Deleted StdDescriptors.c, renamed USB_GetDescriptor() to CALLBACK_USB_GetDescriptor, moved ConfigDescriptor.c/.h from the LUFA/Drivers/USB/Class/ directory to LUFA/Drivers/USB/HighLevel/ in preperation for the new USB class APIs.

Renamed the the TotalHIDReports element of the HID descriptor structure in the HID class demos to TotalReportDescriptors, to be more accurate of the element's function (thanks to Brian Dickman).