Update ReplayGain calculator to be pushed data instead of pulling

That is, instead of calling title_gain() to process
an entire PCMReader, it has update() and next_title() methods
to process FrameLists incrementally.
cd2track and dvda2track calculate ReplayGain at rip time

This saves time vs. waiting until everything is extracted
before calculating ReplayGain.  The old method was an artifact
of performing calculations with external tools like metaflac.
Have cd2track conditionally format output log

That is, it displays abbreviated log headers if the terminal is too narrow
or wider ones if there's enough room.