atomic verify: remote inspect and more details

[baude]

With the remote_inspect function in RH docker, we can inspect
and image on a remote repository for various information like
versions (when present). This allows us to expand atomic
verify to check a local version against a remote version.

atomic verify now can take an image as input (as before) and
provide a greater level of detail when checking each base
image (defined as a non-intermediate image). It now iterates
on those base images looking for update status.

The output of atomic verify has also been changed slightly to
include a verbose option. When invoked, the verify output
will list each base image with its versioning information.

The non-verbose output remains largely the same, where only
base images that have identified updates are put to stdout.
If verbose is not called for by the user but we find base
images with no version information, we output a warning
message and print verbosely anyway.

Updated man page

[rhatdan]

LGTM