Changes

Summary

1. proper self_update for isolated host;
2. renovated macOS tests;
3. support remote_build_history with optional ghc_setup / ocaml_setup;
4. more robust: avoid isabelle_stack invocation in settings script (potentially slow or failing);
5. clarified names;
6. more Haskell operations; tuned;
7. support sub-directories, i.e. structure module names;
8. prefer symbolic path: it is potentially persisted;
9. tuned (see map_index);
10. tuned;
11. simplified proof, moved lemma, added lemma