Invalid MPRIS PlayListId's

[JasonLG1979]

• Operating System: Fedora 26
• Clementine version: 1.3.1

Expected behaviour / actual behaviour

Expected: PlayListId's should start with a reverse DNS of the player.
Example: Pithos PlayListId's start with '/io/github/Pithos/PlaylistId/'
Actual: Clementine PlayListId's start with '/org/mpris/MediaPlayer2/Playlists'
As noted in #5795 the use of object paths that start with '/org/mpris/' is forbidden by spec.

This along with #5797 means that your PlayList interface is broken.

Steps to reproduce the problem (only for bugs)

Get playlists from Clementine.

https://github.com/JasonLG1979/gnome-shell-extensions-mediaplayer/wiki/Known-Player-Bugs#clementine

[JasonLG1979]

Clementine/src/core/mpris2.cpp

Line 498 in e5ab3e7

QString("/org/mpris/MediaPlayer2/Playlists/%1").arg(id));