Allow the user to show the current volume from MPD status via the
`format` and/or `tooltip-format` configuration options.
The values are provided by libmpdclient and are integers, generally
between 0-100 (without %). Values above 100 are also possible, as mpd
output plugins like `pulse` support volumes above 100%.
Signed-off-by: Sefa Eyeoglu <contact@scrumplex.net>
fc89b01ba6