Move the canonical run configuration objects to a sub-package

* Config is now runconfig.Config
    * HostConfig is now runconfig.HostConfig
    * MergeConfig is now runconfig.Merge
    * CompareConfig is now runconfig.Compare
    * ParseRun is now runconfig.Parse
    * ContainerConfigFromJob is now runconfig.ContainerConfigFromJob
    * ContainerHostConfigFromJob is now runconfig.ContainerHostConfigFromJob

This facilitates refactoring commands.go and shrinks the core.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)