Add back support for Google Compute Engine

* Add GCE support complying with @nimiq composable module structure. Does not deploy `biostar` inside yet.
* Slightly simplify docs. Add quickstart section.
* Add `meta` to publish role on ansible galaxy.
* Low-prio TODO: Find a way to deploy ansible-biostar in the most cloud-agnostic way possible (see quickstart in `README.md`).
* ~~Low-prio TODO: Investigate and possibly add Google's kubernetes[1] docker to google compute engine module.~~ We do not need scheduling, just docker.

[1] https://github.com/GoogleCloudPlatform/kubernetes
If I remember well, without this part no outbound ports are open in my AWS. I'll test it right now.