Changes

Summary

1. more accurate spell-checking for nested quotations / antiquotations, notably in formal comments;
2. uniform typesetting of \isamarkupcmt and \isasymcomment;
3. more accurate position for enclosing cartouche;
4. tuned;
5. clarified signature;
6. clarified presentation_state with provide presentation_context;
7. show only symbols with code;
8. clarified markup: more like outer syntax side-comment;
9. clarified rail token language: white space and formal comments;
10. clarified modules;
11. removed duplicate text;
12. clarified exception;