- Added D4 and moved associated SD_CS so that they are paired within list
- Added D7 and SD_CD which is the SD Card Detect pin
- Added D8 and GREEN_LED
- Added RED_LED associated with D13
* Introduce a python script to generate the USB descriptor instead of
a bunch of C macros. In the future, we can use this dynamically in
CircuitPython.
* Add support for detecting read-only mass storage mounts.
Fixes#377
Matt Land
Dan Halbert
Stewart Colborne
Scott Shawcroft