Add presets for metadata-extraction script

[eljamm]

• contacts: returns a list of author e-mails to send the survey
• overview: data to be processed for the projects overview page

[Erethon]

Tested and both -p emails|overview works as expected, LGTM. A minor nitpick, there's some extra whitespace at the end of some lines in extract_project_metadata.py that we can get rid off.

[eljamm]

Nice catch! I turned off formatting for that code block to make it more readable, but that apparently turned off all formatters, not just for Python.