- Store relative path in page objects, remove SNAP_STORAGE_PATH constant and use env variable everywhere, fix some typos in TODOs
- Add document_src, document_id and pages as properties in DocumentDataClass
- Improve DataSnapshot api, add document_dataclasses and get methods
- Images and ocr folders are document ids instead of document src
- Pickled snapshot is saved as `snap.pickle` instead of `snap..pickle`
- Add StoredSnapshotException
- Add src attribute in document, put NoneField in a separate module
- Fix Page repr