Adding deleting old version of textures files when a material is changed

Makefile

@@ -55,6 +55,10 @@ $(SBSAR_DIR)/%.sbsar: $(SBS_DIR)/%.sbs
 	pngfiles="";\
 	material=$$(basename $@ ".sbsar");\
 	echo "material :"$$material;\
+	echo "Cleaning old entries from the material :"$$material;\
+	rm -Rf $(PNG1024_DIR)/$${material}*;\
+	rm -Rf $(PNG512_DIR)/$${material}*;\
+	rm -Rf $(PNG256_DIR)/$${material}*;\
 	for preset in $(PRESETLIST) ; do \
 	echo "- Preset" $$preset; \
 	listitem="";\