Rename console to uart

Rename console to uart

The term "console" felt like a misnomer; the console is really just a
way to access the uart.  A more complete concept of "console" will
include line discipline and similar higher-level concepts.

This is all in preparation to switch over to using Minicom as the
standard interface.  As we head towards running this on hardware, it's
going to make more sense to make the serial terminal experience on
Minicom a good one.