Make clean.py actually work
Update how Houses are resolved
Fix typo in committee resolution function
Improve membership resolution to explicitly generate IDs.
Support posts as part of membership resolution
Include first pass at constituencies represented.
Make cleanup script more robust, also include posts
Make membership of the commons only relate to constituencies
Include post IDs in generated membership IDs.

It's not entirely unreasonable for someone to have two memberships of
the same organisation starting at the same time.
Merge branch 'release/v0.3.0'