AV-OS v0.2.0

I started working on some more changes in the shell. I dropped in two commands: echo & uptime. I changed the Timer interrupt to increment an unsigned 64 big integer, which is displayed on uptime command. I'm not sure how often it increments.... maybe I'll add in a clock in next release. Echo just repeats back the param to you.

There was a bug with shutdown command. It wouldn't shut off QEMU! I didn't try this during my testing, so that's on me. I'll probably add more unit tests to catch stuff like this.

Full Changelog: v0.1.0...v0.2.0