performance improvement from caching setting

I was profiling a client's very large/slow site and I found that a surprisingly large amount of time is spent on this API call. It was less surprising once I thought about it - it's a permission, so it gets called ~2000 times when I view a contact, and settings are much more expensive to look up than CRUD entities because of all the override/MagicMerge.

This cache makes this function run 15x faster.