This is a big performance gain, especially for the tests.
Examples:
----
`./manage.py test galaxy.tests.GalaxyTest.test_full_galaxy_state`
Measurements averaged over 3 run on *my machine*™:
Before: 2min15s
After: 1m41s
----
`./manage.py generate_galaxy_test_data --user-pack-count 1`
Before: 48s
After: 25s
----
`./manage.py rule_galaxy` (for 600 citizen, corresponding to 1 user-pack)
Before: 14m4s
After: 12m34s
Main changes:
- Multiple Galaxy objects can now exist at the same time in DB. This allows for ruling a new galaxy while still
displaying the old one.
- The criteria to quickly know whether a user is a possible citizen is now a simple query on picture count. This
avoids a very complicated query to database, that could often result in huge working memory load. With this change,
it should be possible to run the galaxy even on a vanilla Postgres that didn't receive fine tuning for the Sith's
galaxy.
