Add formal protocol specification

[Jason Gerard DeRose]

In an effort to finalize the version 1 protocol, I've written a more formal protocol specification with test vectors, so that we can get an independent implementation or two before we declare the protocol final.

I've also roughed out the key parts of a C implementation for the sake of clarifying certain details that will be relevant for some languages, and to make sure the protocol isn't usually difficult to implement in C (it's not). Eventually this will be move into a standalone C library aimed at constrained platforms, and aimed at media consumption more than production (phones, tablets, TVs).

[Jason Gerard DeRose (jderose)]

FYI, the specification is now online here:

http://docs.novacut.com/filestore/specification.html