Implement proto toolchainisation

[comius]

Design document: https://docs.google.com/document/d/1CE6wJHNfKbUPBr7-mmk_0Yo3a4TaqcTPE0OWNuQkhPs/edit#heading=h.5mcn15i0e1ch

[alexeagle]

@comius can you assign to @thesayyn - we are going to start on this pretty soon.

[comius]

cc @fowles, @haberman

I've sent invite to @thesayyn, @alexeagle.

There's quite some stuff that needs to be coordinated internally, I'll start pushing out changes.

[alexeagle]

Hm, I don't see any invites from GitHub...