Release Engineering

With the initial uploads to sonatype/maven-central & code debonged & in-place, it would be ideal if releasing final JARs could be made part of the release process.
Releasing the JARs is pretty much a simple 'buck build api_deploy' in a tree with a prior full build, so hopefully this adds ~zero overhead.

A readme is available at solenv/maven/README.md which just needs c&p'ing or linking.