Add new material and texture for cube; update object file with new geometry and material references

cube.mtl

@@ -30,6 +30,12 @@ Kd 0.364706 0.415686 0.466667
 Ks 0.330000 0.330000 0.330000
 map_Kd cube/Denim_03_1K.png
 
+newmtl _
+Ka 0.000000 0.000000 0.000000
+Kd 0.458824 0.333333 0.117647
+Ks 0.330000 0.330000 0.330000
+map_Kd cube/_.png
+
 newmtl Wood_Veneer_15_1K
 Ka 0.000000 0.000000 0.000000
 Kd 0.403922 0.270588 0.176471