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.
Redocumented all device demos, now that they have changed over to the new USB class drivers.
Added C linkage to class drivers for C++ support.
Added prefixes to most of the class driver constants to prevent name clashes.
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.