Do first full release

[cornelius]

When going through our first software release we will need to do some extra checking and setup work. This issue is supposed to track what needs to be done there. The result should be a working and documented release process we can repeat for subsequent releases.

• [ ] Create release notes
• [ ] Tag release (first test release could be v0.0.1)
• [ ] Test gitian builds from tagged release (make sure version numbers are correct, all platforms build, artifacts can be signed)
• [ ] Create GitHub release (add release notes and any other needed information there)
• [ ] Several people: Do Gitian builds and publish signatures of artifacts manifest in dtr-org/unit-e-sigs
• [ ] Check that signatures can be verified and builds are identical
• [ ] When there are enough signatures: Add release builds to GitHub release
• [ ] Adapt script to verify binaries and check that it works (#838)
• [ ] Document release process (adapt doc/release-process.md)