Map "click" event renamed to "singleclick"

As discussed with @tschaub in #1195.

examples/popup.js

@@ -61,7 +61,7 @@ var map = new ol.Map({
 /**
  * Add a click handler to the map to render the popup.
  */
-map.on('click', function(evt) {
+map.on('singleclick', function(evt) {
   var coordinate = evt.getCoordinate();
   var hdms = ol.coordinate.toStringHDMS(ol.proj.transform(
       coordinate, 'EPSG:3857', 'EPSG:4326'));