Introduce eyeo/cms role

This is to support ansible-playbooks.git static-website-1 branch which reimplements eyeo/devops/legacy/infrastructure static web site deployment

Mostly a rewrite of modules/web/manifests/server.pp, whose original authors included Wladimir Palant, Francisco Lópe, Mathias Hennig

The actual generation of content is left out of the default code path, as it can be done once as an initialization from a provision playbook, or as a regular job from within gitlab runner