"" is the correct name of the root directory when mounting a device there
(as opposed to "/"). One can now do os.listdir('/') and open('/abc'), as
well as os.listdir() and open('abc').
Main entry point is _boot.py which checks whether FAT FS in flash mountable,
and if so, mounts it. Otherwise, it checks if flash is empty, and if so,
performs initial module setup: makes FAT FS, configures default AP name,
etc. As a last option, if flash is not empty, and could not be mounted,
it means filesystem corruption, and warning message with instructions is
printed in an infinite loop.
Paul Sokolovsky
Damien George
Josef Gajdusek