Move most of to_html.py from cnx-upgrade to cnx-archive

Remove dependency on cnx-upgrade by moving all code cnx-archive requires
into cnx-archive.
Change MANIFEST.in to reflect the rename of test data dir
Move collection minor version migration from cnx-archive to cnx-upgrade
Move buylink migration from cnx-archive to cnx-upgrade
Merge pull request #75 from karenc/remove-cnx-upgrade-dependency

Move cnx-upgrade dependent elements to this package.