discover metadata about upstream projects

 The upstream ontologist discovers metadata about the upstream part of a
 package by reading common project metadata files. It currently supports:
 .
  * setup.py/PKG-INFO files
  * package.json files
  * package.xml files
  * dist.ini files
  * META.json / META.yml files
  * GNU configure files
  * R DESCRIPTION files
  * pom.xml files
  * Cargo.toml files
  * and other formats