Add subcommands for image-repository

This adds all the standard subcommands for the ImageRepository type.

Following `source`, I have put them under a namespace: `auto`,
referring to automation.

NB For `create` I use controllerutil.CreateOrUpdate, which looks to me
like a slightly more rounded version of the upsert* funcs.

Signed-off-by: Michael Bridgen <michael@weave.works>