Moved DIRECT_ONLY_CATEGORIES from mongo/base.py
Added update_item, create_item, create_child to split_draft.py
Cleaned up TODOs in test_mixed_modulestore.py
Unit test for auto-publish

LMS-11017
Added tests to test_mixed_modulestore.py for has_changes and added black_list to _auto_publish
Moved DIRECT_ONLY_CATEGORIES to draft_and_publish.py