Change features file for twi -> usb pins.
Implement USB (v-usb) support.
First working version with v-usb.

 - Remove watchdog timer for auto pwm mode, there is no guarantee
that the handler will be called in time and the device gets
reset. It's now handled by SOF-counter in main code.
 - Introduce USING_CRYSTAL define to disable RC-calibrating code.
 - Correct ioport definitions to actual test board
Add connectusbraw test program.
Now messages can be sent and received (experimental).
Add real packet testing to connectrawusb.
Improve packet handling.
Move command sense and input sense to "internal_outputs".
Remove last TWI/I2C remains.
Improve packet handling, part 2.
Add delay to flash internal outputs on startup.
Move initial led output flash to after init, to be able
to check if it's still running after init.
New io port assignments for new board.