Merge pull request #74 from karenc/plpy-refactoring-v2

Remove duplicate code by using plpydbapi in plpython code
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