Add portable mode option in settings

[Kyogre]

On Windows OS there is a workaround - you can make whole settings directory portable using argument --user-settings-dir "%CD%\settings" in the link to .bat file.
Thus in the Target of your link you will get something like this:
"C:\...\squirrelsql\squirrel-sql.bat" --user-settings-dir "%CD%\settings"

But it would be great to see an official option in settings.