Manifest listing usability improvements

[agazso]

• Sometimes listing takes a while, it would be good to show a spinner and maybe also print a message. For example with this reference: 35c6c82f3325c3ed1bb9bceb68c413d44ac3d07f6a7d18999b72b6b31534d6f1

• If the reference points to a feed manifest listing without -v prints nothing. It would be better to print out the type of the reference found at the top for all types of references. Also for feed manifests it would be good to have an option to follow the feed (e.g. make a feed lookup and continue the listing on the resolved reference). Example reference: fdfd170f73953bc262d936d3a5329b787980335dc0547032bb2a6239ebe95a76

• It would be good if listing with -v would also print the size of the files.

Feel free to break this issue into separate issues.