rename most wood, metal, etc textures

to bring them all together into one "category" instead of being scattered across the directory
also combine a couple dupes.

homedecor/electronics.lua

@@ -23,7 +23,7 @@ homedecor.register("speaker_open", {
 		"homedecor_speaker_sides.png",
 		"homedecor_speaker_driver.png",
 		"homedecor_speaker_open_front.png",
-		"forniture_black_metal.png"
+		"homedecor_generic_metal_black.png"
 	},
 	groups = { snappy = 3 },
 	sounds = default.node_sound_leaves_defaults(),