Cut version 2.0.0

We've broken backwards compatibility by renaming some options and
changing how the prepare_command and worker_command scripts are
executed. While this perhaps isn't a fancy "shiny and new" major
release, it is in line with the semantic versioning protocol.

Change-Id: I73157abac00e066477df2420315b6173b617e404
Reviewed-on: https://gerrit.causes.com/33872
Tested-by: Shane da Silva <shane@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>