Fix francedata group abbreviations

Add import from FranceData

Apparently I did mistakes with 0.11 and 0.12

Added default pagination for web browser

Representative.addresses.phones is reverse foreign key on a reverse
foreign key so that's impossible to use prefetch_related with.

It would need to be denormalized before being usable, let's wait until
someone requires this specific feature.

Contributed by @luxcem in the first place.

Bugfixes for 0.0.8

Update to remove magic from memopol

remove_countries_without_group and remove_groups_without_mandates are
useful to clean the database before dumping test fixtures