Fix two bugs in hwdoc migrations

Backwards migration 0012 in hwdoc could fail in SQLite due to the
inexistence of an index. Fix it with an if using SQLite. This closes #26
Migration 0016 in hwdoc when run sequentially would create a content
type for Equipment model with no name attribute. Fix it by explicitly
providing a name in the migration. This closes #27
Fix typo in COPYING

Copy paste had the ISC instead of the AUTHOR. Closes #28.
Also in the same commit move the contrib directory one level up. It is
there for license and copyright reasons, no need for people to install
it