migration branches for 5.0

app/controllers/web_migrate.php

app/views/web_migrate/history.php

app/views/web_migrate/index.php

cli/migrate.php

cli/plugin_manager

db/migrations/03_step_87_extern_configurations.php

db/migrations/18_step_00139_upload_file_reorg.php

db/migrations/202011031_add_missing_indices_resources.php

db/migrations/20201103_add_missing_indices.php

db/migrations/20201114_migration_history.php

db/migrations/20210317_change_blubber_thread_following.php

db/migrations/20210322_migration_history_reworked.php

db/migrations/259_migrations_reloaded.php

lib/classes/PluginAdministration.php

lib/classes/StudipCacheFactory.class.php

lib/migrations/DBSchemaVersion.php

lib/migrations/Migration.php

lib/migrations/Migrator.php

lib/migrations/SchemaVersion.php

lib/models/StudipNews.class.php