Nitrogen doesn't correctly detect Desktop window when Conky with own_window used

[daf]

From #86, @holmeslinux was using a Manjaro-JWM desktop that had a few conky windows defined. The conky windows have the own_window = true and own_window_type = 'desktop' settings set, which causes Nitrogen to assume they are some kind of full screen overlay similar to how older Nautilus worked. The fallback mechanism makes Nitrogen pick the X setter via UNKNOWN, which is screwing up Xinerama detection.

I've misinterpreted _NET_WM_WINDOW_TYPE=_NET_WM_WINDOW_TYPE_DESKTOP to mean only full-screen covering style windows which Nitrogen has to detect, not other uses of the property as conky does (correctly). Actual text:

_NET_WM_WINDOW_TYPE_DESKTOP indicates a desktop feature. This can include a single window containing desktop icons with the same dimensions as the screen, allowing the desktop environment to have full control of the desktop, without the need for proxying root window clicks.

Note can.

Will have to refactor the detection mechanism to take WM_CLASS targets that we're actively searching for so we can filter any _NET_WM_WINDOW_TYPE_DESKTOP discoveries and continue searching for more of them.

[daf]

WIP https://github.com/l3ib/nitrogen/tree/rootdetect