Print name of what is being scanned when scanning with --verbose

[agateau-gg]

(this is a follow-up of #211)

When scanning with --verbose it would be useful, when possible, to provide more details on the progress of the scanning process:

• scan path, scan archive and scan pypi should print the filenames
• scan repo and scan commit-range should print the commit ids
• scan docker should print the scanned layers