[Feature] Multi-value fields (breast type, ethnicity, nationality, etc)

[echo6ix]

Is your feature request related to a problem? Please describe. A few fields would be more accurately represented with the capacity to have multiple values. This is related to #210 and expands upon it.

Describe the solution you'd like Add multi-value support for:

1. Ethnicity Applicable performer's could have combos like Asian and Black to accurately reflect them, instead of falling into one of the other or into Mixed, which seems like a catch-all for unknown mixed ethnicity.
2. Breast type Many performers start their career with natural and change to augmented. How can we better reflect that? a. Allowing multiple values b. Allowing multiple values with an adjacent form for date ranges (i.e. "Natural, 2010 - 2015; Augmented: 2015 - 2019")
3. Nationality Somewhat of an edge case, but there are performer's that have dual nationalities. This would apply to people who are born in country a, but raised and are a citizen of country b. This is really pedantic but I thought I'd mention it for accuracy's sake.
4. Hair color See #210

[echo6ix]

Something like this...

Dates for breast type would obviously be optional, but allowing for Natural and Augmented would be more accurate than having to choose one or another when they've had both attributes. Same for hair color.

[sleetx]

This is a great idea and would be a huge improvement in how to track this information. I assume there will need to be some changes on the Stashapp end of things to fully utilize this.