PMIC handling needs to be decided; if we use the SDU method we could have troubles.
Probably the best way is using sercoms directly.
Anyway, the defaults SHOULD be almost ok (except the maximun charging current)

Via 2nd stage boot code that checks SD card for UPDATE.bin

The exported variable is used by banzai() to avoid erasing any bootloader part

This commit enables PWM on pin 11 instead of pin A4 on MKR1000 improving UNO pinout compatibility

Change digitalPinToInterrupt to return pin, and use g_APinDescription[pin].ulExtInt to map pin inside attachInterrupt/detachInterrupt

This brings things inline with the atachInterrupt documentation for
usage:
attachInterrupt(digitalPinToInterrupt(pin), ISR, mode);

Fix #126

The pin mapping is still subject to change, better to not distribute
files that are not final.