cmd: Split commands into their own files

Commands shouldn't all live in main.c.  Move everything except
"help" into its own command file.
scriptic: Support searching by name

Rather than hardcoding scriptic scripts, we can look through all
known script names.
scriptic: Add more complete script debugging

This adds the ability to print out each command as it's executed.

This is a compile-time option.
include: Add GPIO header file

This adds a header file to describe Fernvale's unique GPIO scheme.
spi: Get basic SPI commands working