MPD allows clients to create named "partitions", each with its own
queue, player and outputs. This commit adds controls to allow the user
to create, delete, and switch between partitions.
- Move call to Mpris::updateCurrentSong() downwards to pick up the potential
update of current song's duration from MPD's total time value (introduced
by commit 1a38e468b7) and to avoid duplicate
notifications (cf. commit bba9cfd880).
- Update MPRIS status value CanSeek when MPD's total time changes.
- Set MPDStatusValues::timeElapsed and MPDStatusValues::timeTotal to 0
instead of -1 by default because the latter yields 65535 as these
variables are 16 bit unsigned integer.
