Extract :url and :keywords to package info
Add extra package info to archive index entry
Fix commentary extraction for single file packages

Explicitly read the commentary instead of relying on the package info.
Fixes a regression from changed pkg-info format, and has the added bonus
that it works on 24.4 as well, where pkg-info never contained the
commentary anyway.
Write extra info to descriptors of TAR packages
Merge pull request #1619 from lunaryorn/package-metadata

Include package keywords and URL in archive-contents