Support for high current stepper and other updates

- Bring AdvancedFirmata up to date with StandardFirmata
- Bring Stepper implementation up to date with StepperFirmata in configurable branch of firmata/arduino
- Enable setting a 2 microsecond delay in stepper driver to support high current steppers

The updated stepper config protocol is:
```
STEPPER_CONFIG
0  START_SYSEX
1  Stepper command
2  config command
3  device number
4  interface  lower 4 bits: 1 -> easy driver type, 2 -> two wire config, 4 -> 4 wire config
              upper 4 bits: 1 -> use 2 microsecond delay when stepping (step + dir driver)
...
```

So if you want to use a step + direction driver with a 2 microsecond rather than the default 1 microsecond delay, pass 0x11 as the *interface* parameter.