User preference storage_dir ignored for fotos

[icrf2000]

Fotos go to a fixed directory, regardless of what the user sets as preference prefs_storage_dir.

app/src/main/java/net/osmtracker/db/DataHelper.java:

	public static File getTrackDirectory(long trackId) {
		File _return = null;
		
		String trackStorageDirectory = Environment.getExternalStorageDirectory()  
		+ "/osmtracker/data/files/track" + trackId;

(Really nothing severe... I stumbled over it by chance when testing other stuff.)

[Binnette]

Fixed in #451 #458