.delete_comments() and delete Nag Codes as well as Option Convert them and keep them

[santafiora]

I attached two pgn Files Polgar-Anand.pgn.txt and game_193.pgn.txt

As you can see sometimes NAG Codes are stored in the format $13 and $1 from ....... Polgar-Anand.pgn.txt
and sometimes the are stored like comments in curly brackets (5. d4 {?} ....6. .. Nc6 {! -+}) ...................... from game_193.pgn.txt)

Snippit from Polgar-Anand.pgn.txt
played in his presence by Topalov a couple of weeks before.} (7... h6 8. f4 (
8. h4 $5 8... e5 9. Nf5 g6 10. Nxh6 Bxh6 11. Bxh6 Bxg4 12. Qd2 $13 {
Topalov-van Wely/Monaco act 1999}) 8... e5 $5 9. Nf5 9... h5 $1 {was in the
tre of discussion in 1998. (Shirov-Kasparov/Linares 1998, Svidler-Topalov/
Polgar-Anand.pgn.txt

Snippit from game_193.pgn.txt

1. e4 e5 2. f4 exf4 3. Nf3 g5 4. Bc4 g4 5. Ne5 (5. d4 {?} 5... gxf3 6. Qxf3 d5
   {! -+ Black has a decisive advantage.}) 5... Qh4+ 6. Kf1 Nh6 (6... f3 {
   -/+ Black has the upper hand (Cochrane)}) (6... Nc6 {! -+}) 7. d4 f3 {!} 8. Nc3
   (8. g3 Qh3+ 9. Kf2 Qg2+ 10. Ke3 f6 {?} (10... f5 {

game_193.pgn.txt