Adding PIT support

[schuylermartin45]

For now, it looks like the main project can get away with just using the RTC/CMOS BIOS interrupts to get time. In the future, I would like to do things the "right way" and build a proper interrupt.

I started work in a separate branch to add PIT support but have since abandonded it due to time constraints on the final project.
See commit ade25d1