Auto-Detect SD Card presence/removal

[LIFsCode]

SD card can be detected throuth CD/DAT3 Pin.

• [ ] Check if SD Pin is high --> mount sd card
• [ ] Check if SD Pin low --> unmount sd card
• [ ] Handle SD Pin in an interrupt to react faster
• [ ] Add option to manually mount/unmount SD card e.g. via Bluetooth
• [ ] The SD card should flash maybe one minute or so if no card inside

NOTE: This requires a HW modification!

[EDsteve]

Why didn't i think of that? The SD CD pin was in front of my face all the time. Haha

Schematics have been updated to support this feature and will be implemented in ELOC3.1 SD CD pin is routed to IO4 of the IOextender.

[LIFsCode]

Blocked by #62