Timescale logic fix. Handling of byte-to-chunk logic where byte offset precedes first chunk

The test logic was using the timescale from the MovieHeaderBox instead of the track's
 MediaHeaderBox. So the sync point times were being calculated incorrectly.

Once that was fixed, the time value in the test case preceded the first entry
 revealing an unhandled case where the byte offset from the sync track
 precedes the first chunk in the second track. Added logic for that case.

Fixed up some logging.

Testing with just B-AVC_MP4_MP_SD-03.MP4 for the time-being.