Feature common prefix

This also goes with
https://github.com/gkorf/synnefo/tree/debian-feature-common-prefix
https://github.com/gkorf/pwc/tree/feature-common-prefix
https://github.com/gkorf/pwc/tree/debian-feature-common-prefix
https://github.com/gkorf/snf-image/tree/feature-common-prefix