Update README.md

Update README.md

Add support for jenkinsfile.

Remove bash-ism.

Update the documentation.

Documentation and PATH update.

Add RPM generation node.

Remove unneeded import.

Merge changes from downstream.

Minor bugfix, not all templates have variables.

Add templating engine to make the code much more readable.

Ensure environment is clean, otherwise breakage occurs when running git clone for the second time.

Merge changes from downstream.

Merge changes from downstream.

Update the documentation example to better reflect reality.