Rename ol.source.BingMapsOptions style property to imagerySet

To match the Bing Maps terminology

src/objectliterals.jsdoc

@@ -590,7 +590,7 @@
  * @property {string|undefined} culture Culture.
  * @property {string} key Bing Maps API key. Get yours at
  *     http://bingmapsportal.com/.
- * @property {string} style Style.
+ * @property {string} imagerySet Type of imagery.
  * @property {ol.TileLoadFunctionType|undefined} tileLoadFunction Optional
  *     function to load a tile given a URL.
  * @todo stability experimental

src/ol/source/bingmapssource.js

@@ -38,7 +38,7 @@ ol.source.BingMaps = function(options) {
   this.culture_ = goog.isDef(options.culture) ? options.culture : 'en-us';
 
   var uri = new goog.Uri(
-      '//dev.virtualearth.net/REST/v1/Imagery/Metadata/' + options.style);
+      '//dev.virtualearth.net/REST/v1/Imagery/Metadata/' + options.imagerySet);
   var jsonp = new goog.net.Jsonp(uri, 'jsonp');
   jsonp.send({
     'include': 'ImageryProviders',