Scrobble forwards & specify listening times

[abers]

By default, sounds_scrobble now assumes user is scrobbling after listening to all tracks or a range of tracks - so scrobbles final track for current time and works backwards. Scrobbling forwards will require additional functions - such as a function to calculate total time of all tracks / range and another to specify time started or finished listening. Also, if the user wants to scrobble at the same time as listening to the programme then will need to add waits equal to track-length - with options for pausing or stopping.