SD Card Auto mount/unmount

[johnbaumann]

An attempt is made to mount the SD card at startup, but the status is not polled beyond then. If the card is unexpectedly removed or re-inserted after this time, it should be detected and handled accordingly.

[johnbaumann]

Latest PCB revision has chip-detect pin, assigned to GPIO 2 - LOW = Present, HIGH = Not present

During boot:
Test card communication, test read etc. If CD is HIGH but card read succeeds, do not enable interrupt(bypass CD). Add a global override option for this(maybe add to config too)

During runtime:
Interrupt on any edge. LOW = Mount card, HIGH = Dismount card.

Mount behavior:
Treat as reboot to reload config, wifi settings, default card image, etc? Results in loss of unsaved data held in RAM
-OR-
Maintain card filename and resume write attempts to previous path. May result in unintentionally overwriting existing data.(Maybe don't do silly things like swap SD cards during use!)

The latter seems preferable. Reboot to reload config seems more appropriate(and easier to deal with)