docker2aci: create ACI from Dockerfile about docker2aci

[philips]

I am a bit on the fence having thought this through some more. I can see it being somewhat useful but we could only support a super limited subset of the grammar. It seems better to just leave this task to the docker engine unless someone wants to create something that operates on a chroot and spits out an ACI on every line or something.

[jonboulle]

Yes, this was originally a somewhat speculative feature idea but I am also unconvinced it would necessarily be wise; we should probably just defer to the Docker engine for the build process and focus on the conversion from the built image.

[jonboulle]

Let's stick to letting the Docker engine do its thing and focus on appropriately converting the output images.