C.D. machinery - simplified the retrieval of bintray github API

There is no point using a project property API, env. variables for local testing and development work just fine (we have to use env vars anyhow as Travis uses them).
C.D. machinery - exposed a method for incrementing versions

This way, we can increment versions without invoking the task. This is useful for building a release procedure.
C.D. machinery - reworked the release steps

1. Changed the user to be an artificial 'Continuous Delivery Drone' instead of myself.
2. Added some basic dry-running capabilities (needs more work and tidy-up).
3. Changed the procedure so that there is only one git push at the end.