clarified Skip_Proof.cheat_tac: more standard tactic; clarified Method.cheating: check quick_and_dirty when it is actually applied;

tuned signature and module arrangement;

tuned;

tuned GUI;

centralized various multiset operations in theory multiset; more conversions between multisets and lists respectively

avoid odd foundational terms after interpretation; more uniform code setup

more uniform style for interpretation and sublocale declarations

merged

tuned session specification;

tuned proof;