Summary:
Implement the virtual desktop protocol discussed in
T4457 xml protocol, client and server part.
The PlasmaVirtualDesktopManagement interface manages the desktops
instantiation and layout, each desktop is a PlasmaVirtualDesktop
instance which contains unique id, name and position.
PlasmaWindow has new events: plasmaVirtualDesktopEntered
and plasmaVirtualDesktopLeft when a window enters or leaves a desktop,
and desktops as the list of desktops is in. A window can be on
any subset of desktops, if the list is empty, it's considered on all desktops.
Test Plan: Autotest
Reviewers: #kwin, #plasma, graesslin, hein, davidedmundson
Reviewed By: #kwin, #plasma, davidedmundson
Subscribers: davidedmundson, zzag, bshah, romangg, kde-frameworks-devel
Tags: #frameworks
Maniphest Tasks: T4457
Differential Revision: https://phabricator.kde.org/D12820
