Documentation for docker services

This is WIP I figured I would start it while the feature is in review...
(TLDR; everything as a service does not work well for common use cases and is complicated otherwise)

@jonasfj services need to be run as deamons and started _prior_ to the "primary" task which will be used to determine/mark success/failure I don't think making everything a service will work unless we mark one "service" as primary somehow or come up with a more complex mechanism for linking.

Aside: Docker is adding support for "groups" of services which will be a good alternative for this kind of stuff.