Given an object representing a docker image, in the same format as given by getRegistryAndName, compile it back into a docker image string, which can be used in Docker command etc.
> compileRegistryAndName({ registry: "registry.resinstaging.io", imageName: "resin/rpi", tagName: "1234"})=> 'registry.resinstaging.io/resin/rpi:1234' Copy
> compileRegistryAndName({ registry: "registry.resinstaging.io", imageName: "resin/rpi", tagName: "1234"})=> 'registry.resinstaging.io/resin/rpi:1234'
Given an object representing a docker image, in the same format as given by getRegistryAndName, compile it back into a docker image string, which can be used in Docker command etc.