Adding iOBC UART doc + demo

[CatGarab]

Adding doc blurb about the iOBC's UART ports

Also adding UART TX/RX demo program for KubOS Linux

It's not well fleshed out, but it does work, so I want to save this code somewhere accessible for future reference.

[CatGarab]

iOBC UART communication

[plauche]

Do these programs belong in the examples folder, rather than creating a new demos folder?

[CatGarab]

@plauche Ultimately they could go there, but right now they're rough enough that I don't really want other people to use them. I'd like to come back later and flesh them out with what the options are and how exactly termio works in the context of UARTs.

[CatGarab]

Cleaned the examples up to a point where I'm happy with them. They have now been migrated to the examples folder