appc->oci: get rid of docker2aci

[lucab]

As part of OCI, we will need to get rid of docker2aci conversion when handling OCI, importing them directly.

Current plan is to adopt the c/image library for fetching and storing OCI blobs in native format.

[lucasallan]

@lucab Is it still valuable? I'm wondering if I could work on it.

[iaguis]

@lucasallan I believe this continues to be valuable if you're still up for it.

[poonai]

@iaguis I would like to work on this issue. could you guide me that how can I start?

[glevand]

@Sch00lb0y At a very high level, the first thing would be to get https://github.com/containers/image into rkt/vendor. Then look at the places where docker2aci is used and consider how to convert those to use the the c/image library.