Fixed some long-time issues with file time reading and generating sample
graphs...  It was a bug that only worked because of another bug, and
once the one was fixed, all hell broke loose...

I think this doesn't break backwards compatibility, but it might take a long
time to re-open an old project with audio for the first time.  OTOH, who
would've been using PyDAW for an audio heavy project before now?  This was
probably a good time to break/fix this stuff..