added center to config.js, lets you set map center in world coords

By default, it is set to spawn. Also I changed defaultZoom to 2, which
looks better (the world used to show up as *tiny* by default).

web_assets/functions.js

@@ -256,8 +256,12 @@ function initialize() {
 
     var query = location.search.substring(1);
 
-    var lat = 0.5;
-    var lng = 0.5;
+    var defaultCenter = fromWorldToLatLng(config.center[0],
+                                          config.center[1],
+                                          config.center[2]);
+    var lat = defaultCenter.lat();
+    var lng = defaultCenter.lng();
+    
     var zoom = config.defaultZoom;
     var pairs = query.split("&");
     for (var i=0; i<pairs.length; i++) {