Add S/PDIF optical output to board

[nikitalita]

Adds optical output to the board. Only increases the manufacture price by 2 dollars due to the remapping of the LED pin to S/PDIF output.

No firmware changes yet to enable this; this is just to confirm my design before I send this off to be assembled.

Major changes:

• The LED still exists, but its pin is now used for S/PDIF output. This means it will blink along with the S/PDIF output. This will necessitate some changes to the firmware to make it not just spew all 1s when loading.
• I had to move the power regulator from the front of the board; it's still fairly close to VSYS
• The volume control lines for the wavetable had to be moved to accommodate a better path for the SPDIF line; these run at 250khz so it shouldn't be a problem.
• Various fixes (fixing model paths, adding the bracket to the render, removing non-existent libraries, ensuring symbols exist in project library)