Determine a corresponding source repo(s) (such as Git) for a binary that does not have one obvious

[pombredanne]

Sometimes we have a package that does not have sources or does not have a corresponding source repo (such as a git repo).
We should be able to infer a source repo and possibly a tag or release in this repo based on other available metadata:

• the homepage may be for a GitHub or GitLab repo or some other field
• for instance a description (seen in NuGet packages) or a README may have a GitHub link

We could also infer the tag based on a version, with or without V prefix.

[pombredanne]

@TG1999 ping FYI. We may need this for Maven, npm and NuGet

[TG1999]

Done in #137