Make tileCoordTransform configurable

Instead of using the static createOriginTopLeftTileCoordTransform
function, the correct transform is now a non-API config option of the tile
grid.

src/ol/source/bingmapssource.js

@@ -115,7 +115,7 @@ ol.source.BingMaps.prototype.handleImageryMetadataResponse =
 
   var culture = this.culture_;
   this.tileUrlFunction = ol.TileUrlFunction.withTileCoordTransform(
-      ol.tilegrid.createOriginTopLeftTileCoordTransform(tileGrid),
+      tileGrid.createTileCoordTransform(),
       ol.TileUrlFunction.createFromTileUrlFunctions(
           goog.array.map(
               resource.imageUrlSubdomains,

src/ol/source/tilejsonsource.js

@@ -76,7 +76,7 @@ ol.source.TileJSON.prototype.handleTileJSONResponse = function(tileJSON) {
   this.tileGrid = tileGrid;
 
   this.tileUrlFunction = ol.TileUrlFunction.withTileCoordTransform(
-      ol.tilegrid.createOriginTopLeftTileCoordTransform(tileGrid),
+      tileGrid.createTileCoordTransform(),
       ol.TileUrlFunction.createFromTemplates(tileJSON.tiles));
 
   if (goog.isDef(tileJSON.attribution) &&

src/ol/source/tileutfgridsource.js

@@ -137,7 +137,7 @@ ol.source.TileUTFGrid.prototype.handleTileJSONResponse = function(tileJSON) {
   }
 
   this.tileUrlFunction_ = ol.TileUrlFunction.withTileCoordTransform(
-      ol.tilegrid.createOriginTopLeftTileCoordTransform(tileGrid),
+      tileGrid.createTileCoordTransform(),
       ol.TileUrlFunction.createFromTemplates(grids));
 
   if (goog.isDef(tileJSON.attribution)) {

src/ol/source/xyzsource.js

@@ -41,8 +41,7 @@ ol.source.XYZ = function(options) {
    * @private
    * @type {ol.TileCoordTransformType}
    */
-  this.tileCoordTransform_ =
-      ol.tilegrid.createOriginTopLeftTileCoordTransform(tileGrid);
+  this.tileCoordTransform_ = tileGrid.createTileCoordTransform();
 
   if (goog.isDef(options.tileUrlFunction)) {
     this.setTileUrlFunction(options.tileUrlFunction);