Rewrite pynvcm in Go

[mchack-work]

pynvcm is a hacky solution to write to the internal configuration memory NVCM in the Lattice FPGA we use. It's a bit hard to understand and a bit tricky to distribute to people who want to do their own provisioning.

I propose we spend some time to fully understand the script and then rewrite the whole thing in Go.

We might also want to make it possible for the same tool to write to the SPI flash.

[cibomahto]

See YosysHQ/icestorm#286 for background on how this was created. We were unable to find a public description of the NVCM api, and had to reverse engineer the tcl scripts provided with the lattice programming tool.

[nyabinary]

I feel like Rust would be a better option since it includes some security with it