This means all the sub-subcommands can drop the `image-` prefix,
making them shorter and more fluent.
E.g.,
flux create image policy
rather than
flux create auto image-policy
Signed-off-by: Michael Bridgen <michael@weave.works>
The export command works the same way for most (all?) types. I have
made it generic and moved it into export.go, then ported
{export,create}_auto_image{repository,policy}.go to use it.
Signed-off-by: Michael Bridgen <michael@weave.works>
