Improve cave render - finish 'onlyiflit' support

src/main/java/org/dynmap/hdmap/IsoHDPerspective.java

@@ -240,6 +240,10 @@ public class IsoHDPerspective implements HDPerspective {
          * Get pixel Y coordinate
          */
         public final int getPixelY() { return py; }
+        /**
+         * Get map iterator
+         */
+        public final MapIterator getMapIterator() { return mapiter; }
         /**
          * Return submodel alpha value (-1 if no submodel rendered)
          */