Add json response and versioning to REST API

[vnugent]

1. With the exception of '/containers' currently REST API calls don't return useful json responses. For example I want to inspect a container to find out what public end points are.
2. API version would also be good. Ex: curl http://localhost/api/v1/containers

[smarterclayton]

Part of the gap with /containers is that the original design assumption would be that the caller would be able to remember most of what they sent. I think that's something we should change and improve.

API versioning is actually supported today (it's not on a URL, which I'd like to do) - see https://github.com/openshift/geard/blob/master/http/server.go#L73 which is where we check the API version (X-Api-Version) and https://github.com/openshift/geard/blob/master/http/client/client.go#L35 which is where the remote job is required to define the job version. Currently we're not enforcing version, but I'd like to be able to support multiple implementations and remote versions of the job directly. Agree this should be improved.