Feature request: CRUD on Manifests

Today's implementation of docker manifest is not able to perform following tasks:

• create empty manifest list (useful before loops in image building scripts)
• overwrite existing manifest list (allow building scripts to overwrite previous half-baked manifests and start from scratch)
• list locally created manifests
• delete local manifest lists, pushed or not
• remove local image manifest from manifest list
• clear the annotations for selected image

To solve those, I'm proposing a bit of a changes to manifest commands:

• manifest create MANIFEST_LIST [MANIFEST...] [flags] - creates manifest list, possibly empty.
  Flags can be:
  • --overwrite - remove previous and create new list
• manifest list and manifests - list all local manifests
• manifest delete MANIFEST_LIST
• manifest prune - delete all local manifests, after confirmation
• manifest add MANIFEST_LIST MANIFEST [annotations] - add local image manifest to a list, possibly with annotations, in format as defined today.
• manifest annotate MANIFEST_LIST MANIFEST [flags] [annotations]. Same as today, add/overview annotations for already added image.
  Flags:
  • --clear - delete all previous annotations for selected image manifest, and then add ones from the list. manifest annotate MANIFEST_LIST MANIFEST --clear (without new annotations) would, effectively clear all annotations.
• manifest rm MANIFEST_LIST MANIFEST [MANIFEST...] - remove local image(s) manifest from a list.

Thanks!

Start by reading the existing docker manifest command implementation and its current create and annotate behavior; the issue names no files or tests. Done means supporting the listed create, list, delete, prune, add, annotate, and rm operations, including empty or overwrite creation and annotation clearing.