Allow specific fields to have fallback

[JoseOrtiz]

Hello, I'm having issues with some values that are translated (specifically boolean types), so I decided to remove fallback on settings, but then I realized that I only needed for certain fields to have fallback value, like name, not everything in model. Can you add a settings so you only have certain fields to have fallback values?

[benzkji]

This seems like a common use case, and would be nice to be configurable, without using model.field_language hacks, or custom templatetags. I for example, have a translated "SEO Text" field, that should have no fallback, whereas the rest of the model should fallback as usual.

Configuring this on each TranslationOptions would be nice.