lib/common: add a common.ParsedDockerURL type
lib/common: add a common.ParsedDockerURL type

ParsedDockerURL was part of the internal package so a user that wants to
write a function using that type can't do it because they're not able to
import the internal package.

Define the type docker.ParsedDockerURL as common.ParsedDockerURL.

dgonyeo/docker2aci,jsoriano/docker2aci,OMWAVE/docker2aci,jonboulle/docker2aci,vishvananda/docker2aci,appc/docker2aci,jsoriano/docker2aci,dgonyeo/docker2aci,vishvananda/docker2aci,OMWAVE/docker2aci,appc/docker2aci,iaguis/docker2aci