[RFC] A Forge for Foreman plugins


There were discussions around a Forge on irc and community demos, so I
wrote some thoughts by filling up an RFC. Its light on exact
implementation details for now, but that can be expanded upon once we
identify what we want from the service. Feedback is welcome either
here or directly on the PR[1].

[1] https://github.com/theforeman/rfcs/pull/30