remove combined {models,sprites}.mat, remove extra .mdl .spr exts

bshift/pbr/models/shell.mdl/shell.mat

@@ -0,0 +1,24 @@
+
+{
+"for" "#models/shell/back.mdl"
+//"basecolor_map" "back.png"
+//"normal_map" "back_normal.png"
+//"metal_map" "back_metal.png"
+//"roughness_map" "back_roughness.png"
+}
+
+{
+"for" "#models/shell/bulletCHROME.mdl"
+//"basecolor_map" "bulletCHROME.png"
+//"normal_map" "bulletCHROME_normal.png"
+//"metal_map" "bulletCHROME_metal.png"
+//"roughness_map" "bulletCHROME_roughness.png"
+}
+
+{
+"for" "#models/shell/front.mdl"
+//"basecolor_map" "front.png"
+//"normal_map" "front_normal.png"
+//"metal_map" "front_metal.png"
+//"roughness_map" "front_roughness.png"
+}