compositor-wayland: Parse [output] config sections and more options

This commit makes the wayland backend search through the config for
[output] sections with names starting with "WL" and create outputs
accordingly.  Outputs created due to the config file support mode, scale,
and transform parameters.  It also listens for the --output-count
command-line option.

This brings the wayland backend almost up to par, in terms of functionality
with the X11 backend.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
diff --git a/src/compositor.c b/src/compositor.c
index 134793c..2126742 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -3700,6 +3700,7 @@
 		"  --width=WIDTH\t\tWidth of Wayland surface\n"
 		"  --height=HEIGHT\tHeight of Wayland surface\n"
 		"  --use-pixman\t\tUse the pixman (CPU) renderer\n"
+		"  --output-count=COUNT\tCreate multiple outputs\n"
 		"  --display=DISPLAY\tWayland display to connect to\n\n");
 
 #if defined(BUILD_RPI_COMPOSITOR) && defined(HAVE_BCM_HOST)