Move migrations from commerce_kickstart_migrate into parent modules

bojanz: Haza`: we have multiple problems there. 1) The groups code is a big ugly and hard to understand at first (subjective) 2) Migrations for both demo_store and no_demo_store are registered, which is a bit of a WTF (especially if you install migrate_ui or decide to use Migrate later) since some of them can't ever be used (no matching data structure) 3) To distingush a demo_store product migration from a non_demo_store product migration, we need to add some sort of a prefix to the machine name
bojanz: Haza`: 4) If you uninstall a module (merchandising, for example), the matching migration doesn't get unregistered
bojanz: Haza`: my idea is simple, bundle each matching migration with the actual module for which the migration is intended
bojanz: Haza`: that way you don't need groups and you don't need to filter the migrations during install at all
bojanz: Haza`: commerce_kickstart_product just gives you its migrations, and that's it. Same for others
bojanz: Haza`: fixes all of the problems above and simplifies the code
bojanz: so each module gets an import folder with images and csv(s)
bojanz: and a module.migrate.inc