Also replace use of PINMUX_DEFAULT with PINMUX_UNUSED to prevent any
accidental pin changes. This caused user SPI to break internal SPI
flash on the Feather M0 Express.
Fixes#100
* Track status pin use by user code separately so it can take over the pins and then give them back.
* Switch to hardware SPI for APA102 on Gemma and Trinket.
* Merge microcontroller/types.h into microcontroller/Pin.h to better match approach going forwards.
