WIP: No SELF in lambda
This is based on !24 but takes it a bit further... perhaps too far? I'm not really saying this is the way to go. I was just experimenting.
Many of the contracts_coq are currently broken. I think it is maybe related to the
simplify_instruction tactic, but I did not understand the problem yet.
Compared to !24, this forbids SELF in lambda, and eliminates the "alien" terms resulting from the (non-parametric) quantification over the self type. These do not seem like big problems. I just had this solution in my head from past attempts to precisely formalize "the Michelson type system".