Added new Printer Host mode ClassDriver demo.

Added table of supported classes and modes to the main USB Class Driver documentation.

Add in new invalid event hook check targets to project makefiles to produce compilation errors when invalid event names are used in a project.

Re-add in flip, flip-ee, dfu and dfu-ee targets to project makefiles (thanks to Opendous Inc.)

Fix allowable F_CPU values comment in project makefiles.

Renamed parameters of SI_Host_ConfigurePipes() to match other Host mode Class drivers.

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 Serial_Stream driver to SerialStream to remain consistent with the rest of the library's naming scheme for files.