Add configuration (config.h) file and helpers for a debug console

config.h: General configuration options
blackbox.h: Helpers functions and definitions for debugging over a console.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Implement a debug console over UART0

Implement a debug console to allow sending debug messages.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>