Port to xfconf

The internal XtmSettings object is retained so we don't have to refactor
everything, but the backend now uses Xfconf over the rc file.

src/Makefile.am

@@ -13,6 +13,7 @@ xfce4_taskmanager_CFLAGS =						\
 	$(GTK3_CFLAGS)							\
 	$(WNCK_CFLAGS)							\
 	$(LIBXFCE4UI_CFLAGS)				\
+	$(XFCONF_CFLAGS)						\
 	$(NULL)
 
 xfce4_taskmanager_LDADD = 						\
@@ -22,6 +23,7 @@ xfce4_taskmanager_LDADD = 						\
 	$(GTK3_LIBS) 						\
 	$(WNCK_LIBS)						\
 	$(LIBXFCE4UI_LIBS)			\
+	$(XFCONF_LIBS)					\
 	$(NULL)
 
 xfce4_taskmanager_SOURCES =						\