Remove Repository, Revision and GitRef models

arkindex/documents/api/elements.py

arkindex/documents/export/structure.sql

arkindex/documents/export/worker_version.sql

arkindex/documents/fixtures/data.json

arkindex/documents/management/commands/bootstrap.py

arkindex/documents/management/commands/build_fixtures.py

arkindex/documents/management/commands/load_export.py

arkindex/documents/tests/commands/test_cleanup.py

arkindex/documents/tests/commands/test_load_export.py

arkindex/documents/tests/tasks/test_corpus_delete.py

arkindex/ponos/tests/test_api.py

arkindex/process/admin.py

arkindex/process/api.py

arkindex/process/builder.py

arkindex/process/managers.py

arkindex/process/migrations/0001_initial.py

...ker_repository_url_workerversion_revision_url_and_more.py

arkindex/process/migrations/0041_drop_old_git_references.py

arkindex/process/models.py

arkindex/process/serializers/git.py