#12 disc id calculation

[JobeC]

I noted that the calculated id was slightly off in many of my discs, and started inspecting what was the cause. It turned out that in DiscID.py the total_time should be calculated without the frames. Or at least it seemed to work with the discs I tried it with. I.e., editing the disc_id function, add variable:
track_secs = []

in the track loop, store the seconds, too:
track_secs.append(min*60 + sec)

also, after fetching the leadout info:
track_secs.append(min*60 + sec)

and finally the total time calculation:
total_time = track_secs[-1] - track_secs[0]

With my limited knowledge about Python, I don't understand why this produces different result from using (frames // 75), but I can live with the mystery :)