Don't read all dirs at startup.

include/playlist_manager.h

@@ -13,7 +13,6 @@ class PlaylistManager {
 
 	public:
 	PlaylistManager();
-	std::vector<String> dirs;
 	std::map<String, String> map;
 	Playlist get_playlist(String rfid_id);
 	bool has_playlist(String rfid_id);