* USB fixes:
* USB initialized when USB cable is inserted and de-initialized when disconnected (this was the original way, which proved itself unreliable in the past. Now with the new USB library it appears to work without any problems. Used in this way result in safer operation - USB controller is disabled while unconnected)
Works without force device mod
* Serial: initialization of global variables
* Reduced RAM usage - data moved to FLASH
* Detailed USB interrupt counters (+ debug print fix)
