Improve collection and presentation of authors/holders/copyrights for packages

[pombredanne]

When scanning https://registry.npmjs.org/mime-types/-/mime-types-2.1.35.tgz as package, I would like the better understand who are the package authors. This could mean some of these:

• ensure that the package "parties" to become the package Author(s) when relevant
• aggregate key files authors (possibly from a scan summary as per Add authors to summary scancode-toolkit#3389 )
• aggregate all other authors
• display authors in the pie charts