Change the way a filepath is displayed

Instead of displaying the complete path, display the file name
first and then the path enclosed in parenthesis.

In this way files with same name but different path can still be
distinguished and, at the same time, files with different names
but same path are more easily spotted in case the complete path
is truncated by file managers.

src/support/FileName.cpp

@@ -748,7 +748,8 @@ docstring const FileName::absoluteFilePath() const
 
 docstring FileName::displayName(int threshold) const
 {
-	return makeDisplayPath(absFileName(), threshold);
+	return from_utf8(onlyFileName()) + " ("
+		+  makeDisplayPath(onlyPath().absFileName(), threshold) + ")";
 }