Scan Folder dialog now remembers last location

When you add a new scan folder location it will now remember the last location used so you can add a bunch of folders in a row easily.
You might have missed my previous comment because it got overwriteen when you pushed. It follows.
>Also please move them down, to be together with the other ScanDirs methods. (search for the setDownloadInScanDirs() method.

I mean the getScanDirsLastPath()/setScanDirsLastPath() methods.