Multichamber fixes and tests update #MemopolMiniHackaton

REMOVE DB.SQLITE

Fix tests on master

See the 2 previous commits for example reasons to do that !

0.3.0 introduces status_code generation which causes the test to fail
with FixtureCreated on travis.

Otherwise tests might become broken as a side effect of an upgrade in
these packages. And that's hard to figure out ;)

Fixed url conflicts

Display votes with recommendation only

Added proposal autocomplete, upgrade to DAL v3

Added API

Use Country.get_absolute_url in templates

Also, use django-responsediff instead of manually updating test
fixtures.

Release

3 instances:

- master-memopol.lqdn.fr for the master branch,
- lqdn-memopol.lqdn.fr for the lqdn branch,
- pr-memopol.lqdn.fr for the pr branch.

This is completely backward-incompatible and was rushed before the
release - nobody was going to pay the interrest on the technical debt
this commit remove to support migrations since nobody has an instance in
production.

Memopol{Representative,Vote,Dossier} subclasses are gone. Django model
inheritance is fun but comes at a price - hacks like
create_child_instance_from_parent would end up everywhere. Use a simple
one to one relation when you don't intend to have several subclasses of
a model which is the case here.

Country and current mandates are not pre-calculated and stored in the
database anymore, instead they are pre-fetched which requires
django-representatives>=0.0.7

Score related code was rewritten in votes.models, along with the
Recommendation model. We're still not calculating it on the fly here
because that would require some SQL backflips which will take a bit of
time to do properly.