Split build_and_deploy into build_for_deploy (builds, uploads to S3,
rsyncs manifests) and a deploy script in client-downloads (updates
updates JSON, updates incrementals, runs deploy command).
Release scripts support -b flag for build-only (deploy later manually).
Beta/dev/test scripts build and deploy automatically via SSH.
Move incrementals files from S3 to deploy server. Update DEPLOY_PATH to
root of client-downloads so manifests and deploy script paths are
derived from it.