prefer separate command for approximation

removed junk from library theory

note of_class rule for type classes in theory: useful to promote class instance proofs to locale interpretation proofs

normalizing of type variables before evaluation with explicit resubstitution function: make nbe work with funny type variables like \<AA>; tuned naming; dropped dead parameters;

tuned GUI;

clarified detach_operation: ignore empty output;

bounce focus back to main text area -- Output is for output, not query input;

update for release;