Early Draft of the new Static IFT Specification

I've published an early draft of the new IFT specification which will
eventually replace the prior patch subset and range request approaches. The
draft can be found here: https://garretrieger.github.io/IFT/Overview.html

The draft is incomplete, most notably missing specification for the format
2 mapping table. However, it is complete enough to demonstrate how the full
approach will work. I figured I'd send this out in advance of the working
group call next week, where we could discuss any early feedback on the
draft.