Add uploader next to author/maintainer in info json

[MartinThoma]

I've noticed that on https://pypi.org/project/identifier/ I can see the user "Collie" as maintainer, but on https://pypi.org/pypi/identifier/json the user cannot be seen at all.

It would be nice to be able to get the same information in a structured way as via the GUI.

I'm uncertain if the uploader email is kept confidential.