This has been a long time coming, but we now finally keep track of ReplayGain
values in the database. This is an intermediate step toward a refactoring of the
RG plugin; at the moment, these values are not actually saved!
We now always calculate album gain when importing an album. This is "free" (no
performance cost) now and players are free to ignore the setting if they so
choose.
This ensures accurate album-level data. It also fixes a problem with the old way
of doing things where the MediaFiles and tool results would become misaligned if
a subset of the tracks needed recalculation.
Invocations of the mp3gain/aacgain commands are now wrapped in a centralized
function that takes care of output capture and error handling. This avoids code
duplication for the various sites at which the tool needs to be invoked.
This change also avoids unintentionally modifying tags via the command-line
tool. The "-s s" option makes the tool *just* calculate RG values rather than
toying with tags at all.
