Continuous delivery made possible

Review Jenkins jobs:

• Rename Drive-beta to Drive-build: to create either alpha or beta releases.
• Add Drive-deploy: to convert an alpha to beta, or a beta to release GA
• Remove Drive-prod
• Drive-cleanup does not need a jenkinsfile, it can be converted to a simple job instead of a pipeline

Also, some simple work to do in the tag naming (alpha-xxx for alpha, beta-xxx for beta and release-xxx for release GA).

With those simple changes, we will be able to publish almost any alpha version to a release GA. This means, if we are completely mads, we could be able to have a one-day release cycle:

• each alpha is automatically generated at midnight
• we could promote this alpha to beta with 2 weeks of testing (a complete sprint)
• at the end of those 2 weeks, it all is fine: promote the beta to release GA
• Repeat the next day.
  But this is not what we want, it is only for demo purpose.