DlgTrackInfo - add button to open track in file browser

nope
cdUp just work for valid directories.
It means that if the initial trackDir is non-existent... cdUp will not work!

```
Changes directory by moving one directory up from the QDir's current directory.
Returns true if the new directory exists and is readable; otherwise returns false. Note that the logical cdUp() operation is not performed if the new directory does not exist.
```
http://qt-project.org/doc/qt-4.8/qdir.html#cdUp