Combine the Django migrations under involvement

[Marmingen]

Description

There are dozens of small migrations under involvement that could easily be combined into a single migration.

Steps to Reproduce

1. be in involvement path
2. manage.py squashmigrations app_label [start_migration_name] migration_name
3. delete the now obsolete migration files
4. check dependencies and make sure they now refer to the squashed file
5. if dependencies are all OK: remove the replaces attribute in the Migration class

[Marmingen]

most of them seem to do the same thing as well