Add host mode USB Class driver stubs, add beginnings of a CDC host class driver.

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.

Demos/Device/ClassDriver/Keyboard/Descriptors.h

@@ -41,7 +41,7 @@
 		#include <avr/pgmspace.h>
 
 		#include <LUFA/Drivers/USB/USB.h>
-		#include <LUFA/Drivers/USB/Class/Device/HID.h>
+		#include <LUFA/Drivers/USB/Class/HID.h>
 
 	/* Type Defines: */
 		/** Type define for the device configuration descriptor structure. This must be defined in the