Bringing in FatFs R0.10

Source files as downloaded from
http://elm-chan.org/fsw/ff/00index_e.html
Brought in proper SPI functions and added SD operation

- Removed unused SPI functions and inlined them
- Set DAC SPI back to automatic CS control for speed
- Removed UART code completely
- Removed fatfs placeholder diskio functions
- Switched back to updating DAC in the interrupt
- Changed DAC update to hold galvo position if output is off
- Temporarily disabled USB