v20.6.0

[bmaltais]

- Increase max LoRA rank (dim) size to 1024.
- Update finetune preprocessing scripts.
    - ``.bmp`` and ``.jpeg`` are supported. Thanks to breakcore2 and p1atdev!
    - The default weights of ``tag_images_by_wd14_tagger.py`` is now ``SmilingWolf/wd-v1-4-convnext-tagger-v2``. You can specify another model id from ``SmilingWolf`` by ``--repo_id`` option. Thanks to SmilingWolf for the great work.
    - To change the weight, remove ``wd14_tagger_model`` folder, and run the script again.
    - ``--max_data_loader_n_workers`` option is added to each script. This option uses the DataLoader for data loading to speed up loading, 20%~30% faster.
    - Please specify 2 or 4, depends on the number of CPU cores.
    - ``--recursive`` option is added to ``merge_dd_tags_to_metadata.py`` and ``merge_captions_to_metadata.py``, only works with ``--full_path``.
    - ``make_captions_by_git.py`` is added. It uses [GIT microsoft/git-large-textcaps](https://huggingface.co/microsoft/git-large-textcaps) for captioning. 
    - ``requirements.txt`` is updated. If you use this script, [please update the libraries](https://github.com/kohya-ss/sd-scripts#upgrade).
    - Usage is almost the same as ``make_captions.py``, but batch size should be smaller.
    - ``--remove_words`` option removes as much text as possible (such as ``the word "XXXX" on it``).
    - ``--skip_existing`` option is added to ``prepare_buckets_latents.py``. Images with existing npz files are ignored by this option.
    - ``clean_captions_and_tags.py`` is updated to remove duplicated or conflicting tags, e.g. ``shirt`` is removed when ``white shirt`` exists. if ``black hair`` is with ``red hair``, both are removed.
- Tag frequency is added to the metadata in ``train_network.py``. Thanks to space-nuko!
    - __All tags and number of occurrences of the tag are recorded.__ If you do not want it, disable metadata storing with ``--no_metadata`` option.