[wip] remove duplicate function displayablePorts
fix import after removing duplicate function
move Config and HostConfig to api/
pkg/opts: a collection of custom value parsers implementing flag.Value

This facilitates the refactoring of commands.go.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Merge branch 'api-validate-host' into separate-api-client