Let the tile data pack cache images so we aren't reloading them for various individual tiles within the image. Also, a couple minor efficiency improvements elsewhere.

git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@949 ed5b42cb-e716-0410-a449-f6a68f950b19

src/as/com/threerings/miso/client/MisoScenePanel.as

@@ -272,8 +272,6 @@ public class MisoScenePanel extends Sprite
         _objScene.layoutRenderer = new ClassFactory(PrioritizedSceneLayoutRenderer);
 
         refreshBaseBlockScenes();
-
-        _isoView.addScene(_objScene);
     }
 
     /**

src/as/com/threerings/miso/client/SceneBlock.as

@@ -73,6 +73,7 @@ public class SceneBlock
         var y :int = getBlockY(_key);
 
         _baseScene = new IsoScene();
+        _baseScene.layoutEnabled = false;
         for (var ii :int = x; ii < x + BLOCK_SIZE; ii++) {
             for (var jj :int = y; jj < y + BLOCK_SIZE; jj++) {
                 var tileId :int = model.getBaseTileId(ii, jj);