Feature/Conversion from `material_as_recorded` to `material`

[demery]

The input CSV has two columns for support: material and material_as_recorded. The idea being that an authorized value (or values for MSS with mixed support media, like paper and parchment) would be used for material.

There are a number of tasks:

• Determine whether the model makes this distinction. It does!
• If yes, Identify a vocabulary/authority for material and
• Come up with a method to convert from material_as_recorded to material.

[lpcoladangelo]

Potential controlled vocabularies for materials:
Art and Architecture Thesaurus (AAT): https://www.getty.edu/research/tools/vocabularies/aat/
Thesaurus for Graphic Materials (TGM): https://www.loc.gov/pictures/collection/tgm/

AAT, as a Getty vocabulary, has a reconciliation service already implemented through OpenRefine.
TGM, as a Library of Congress vocabulary, does not (to my knowledge). So one would have to be scripted, I believe.