Wayland support

[thm-unix]

[thm-unix]

Currently plainDE does not support Wayland. There are some unsupported applets (Keyboard Layout, Window List) and other general problems (i.e., inability of moving panel on arbitrary position). We use KWindowSystem::windows() for getting window list (which works only for Xorg/XWayland) and xkb for getting & setting keyboard layout. Both of these approaches are not applicable to Wayland. We will have to write own Wayland compositor to fix all these problems. But since Wayland isn't completely ready yet, we will also have to write own window manager for Xorg. We hope to support Wayland in future, but not now.