Binary USM IR format

[RealA10N]

Create an allow input and output of a binary representation of USM source code.
This should be very computer-oriented, to allow easy integration of USM as a backend of any high-level compiler.

I think we should still hold only a single internal representation, and the current internal representation is very "text source" oriented, so a heavy refactor is required. Perhaps we might want to do that when we move to a new implementation, not in golang.