Remove unused code

- The old character select scene, which was never shown but loaded
  every character image at startup
- Unused SyncResponse and ProgressResponse classes
- Playlist.set_last_played_answered and select/local-loading code in
  the new character select, none of which were called
- Settings.delete_player_children, identical to delete_children
- An unused variable holding a local file path

Player.gd

@@ -60,11 +60,6 @@ func minus_point() -> void:
 func change_character() -> void:
 	change_character_clicked.emit()
 
-func character_selected(file_name: String) -> void:
-	print("Back in player list with: " + file_name)
-	player_object.character = load("res://characters/" + file_name)
-	set_player_character()
-	
 func new_character_selected(character_texture: ImageTexture) -> void:
 	print("Back in player list with new")
 	player_object.character = character_texture