- added function to mark a channel for swapping + swap with current channel

- replaced misuse of "FileLoadException" with a custom LoaderException to handle file loading issues with better continue/fail logic
- removed "Save As" and replaced it with "Convert list" menu item that shows information on how to use a reference list instead of direct conversion

source/ChanSort.Loader.Sharp/SharpSerializer.cs

@@ -246,7 +246,7 @@ namespace ChanSort.Loader.Sharp
           }
         }
       }
-      throw new FileLoadException("File does not contain the expected 3 header lines");
+      throw LoaderException.Fail("File does not contain the expected 3 header lines");
     }
 
     #endregion