Correctly getting tile data for a location.

The UTFGrid layer's `getTileInfo` method was not correctly handling dateline wrapping (and was a bit more complicated than it needed to be).  Since it would be useful to all grid layers to be able to retrieve a tile and pixel offset for any map location, this functionality deserves to be on the Grid layer.

The WMTS layer currently exposes a `getTileInfo` method that is used within the layer and by the WMTSGetFeatureInfo control.  This method could be renamed to `getRemoteTileInfo` or something to differentiate it from a method that gets locally cached tile info.  Until that change is made, the method on the Grid layer will be called `getGridData`.

examples/utfgrid-geography-class.js

@@ -6,7 +6,7 @@ var osm = new OpenLayers.Layer.XYZ(
         "http://otile3.mqcdn.com/tiles/1.0.0/osm/${z}/${x}/${y}.png",
         "http://otile4.mqcdn.com/tiles/1.0.0/osm/${z}/${x}/${y}.png"
     ],
-    {transitionEffect: "resize"}
+    {transitionEffect: "resize", wrapDateLine: true}
 );
 
 var utfgrid = new OpenLayers.Layer.UTFGrid({