Delete player in a PGN file

[fsmosca]

• Create "Delete Player" submenu under Tools menu on Neutral mode.
• Create new window when Delete Player is pressed.
• Create Text, Input, and FolderBrowse elements for pgn loading.
• Create Listbox element to display player names from the PGN file.
• Create OK button.
• Read pgn file and extract player names and show it in Listbox.
• If user selects a player from Listbox delete that player when user pressed OK button.