add additional subfolder structures for the user to pick from

[x-CK-x]

this entails the option to let the user have their data stored in subfolders either via the artist names or character names.
i.e. if the user downloads by concept, then it would look like:

• concept data:
  • by_[artist_name]

or:

• concept data:
  • [character_name]

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The user could also download by artists and have the subfolders be by character or the opposite.

[x-CK-x]

one addition to that could be to create additional subfolders for the artist category if the user also wants to separate style data via a specific year OR timeframe.
i.e. it could like one of the following:

• artist_name:
  • [character_name]
    • [specific_year]

or:

• artist_name:
  • [specific_year]

or:

• artist_name:
  • [character_name]
    • [range_of_years]

or:

• artist_name:
  • [range_of_years]

[x-CK-x]

and the gallery would have to track paths differently, but it would read from all the subfolders in the same manner as it already does.

[x-CK-x]

will need to add these separately to the UI and pass them through to the batch_downloader script.
most of the critical handling of the data will be in the gallery/stats/custom_data scripts; most of the validation will be there.