CamelCase image.Image json marshalling

[vbatts]

This fixes #6340

[vbatts]

ping @vieux

[vieux]

I think the image struct is stored on disk no ? I don't think we can change it ?

[crosbymichael]

On disk and in the registry. We would have to support both keys

[vbatts]

this is a problem. We're going to break something either way, i think.
Or we change docker save to not Unmarshal the json, just dump the json that is disk. And define the contexts that json is manipulated. Because now looking at it, if you

#> docker pull scratch:latest
Pulling repository scratch
511136ea3c5a: Download complete
#> cat /var/lib/docker/graph/511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158/json
{"id":"511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158","comment":"Imported from -","created":"2013-06-13T14:03:50.821769-07:00","container_config":{"Hostname":"","User":"","Memory":0,"MemorySwap":0,"CpuShares":0,"AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"PortSpecs":null,"Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":null,"Dns":null,"Image":"","Volumes":null,"VolumesFrom":""},"docker_version":"0.4.0","architecture":"x86_64"}
#> docker save scratch:latest | tar x
#> cat 511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158/json
{"Architecture":"x86_64","Author":"","Comment":"Imported from -","Config":null,"Container":"","ContainerConfig":{"AttachStderr":false,"AttachStdin":false,"AttachStdout":false,"Cmd":null,"CpuShares":0,"Cpuset":"","Domainname":"","Entrypoint":null,"Env":null,"ExposedPorts":null,"Hostname":"","Image":"","Memory":0,"MemorySwap":0,"NetworkDisabled":false,"OnBuild":null,"OpenStdin":false,"PortSpecs":null,"StdinOnce":false,"Tty":false,"User":"","Volumes":null,"WorkingDir":""},"Created":"2013-06-13T14:03:50.821769-07:00","DockerVersion":"0.4.0","Id":"511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158","Os":"","Parent":"","Size":0}

These are completely different, with regard to formatting of keys. Which means the consistent of this image's metadata has changed. Furthermore, this means the tarsum of this image is now different as well.