De-simplify struct accessor to prepare for impersonators/chaperones
More work on impersonators for structs
Remove redundant import
Make ref/set operations on structs continuations
Restructure various struct implementations to have a common base class
Simplify struct type lookup
Add impersonate-struct and do some cleanup
Simplify some struct code
Add chaperone for structs
Store immutables for a struct as a Python list rather than as Cons cells
Remove useless equal methods from impersonators/chaperones
Consider implementing these as continuations
Get usage of immutables past the translator
Put proper type constraints on method calls for structs