Show a warning if the instance path contains a '!'

The checks and warnings happen the time MMC loads (via QLOG_INFO), the time the GUI starts (via a dialog) and when the user changes the instance path via the settings window.

depends/util/src/pathutils.cpp

@@ -144,3 +144,11 @@ void openFileInDefaultProgram(QString filename)
 {
 	QDesktopServices::openUrl(QUrl::fromLocalFile(filename));
 }
+
+// Does the directory path contain any '!'? If yes, return true, otherwise false.
+// (This is a problem for Java)
+bool checkProblemticPathJava(QDir folder)
+{
+	QString pathfoldername = folder.absolutePath();
+	return pathfoldername.contains("!", Qt::CaseInsensitive);
+}