Add new cacheSize option to ol.source

Option added to:
 - olx.source.BingMapsOptions
 - olx.source.MapQuestOptions
 - olx.source.OSMOptions
 - olx.source.StamenOptions
 - olx.source.TileArcGISRestOptions
 - olx.source.TileImageOptions
 - olx.source.TileJSONOptions
 - olx.source.TileWMSOptions
 - olx.source.VectorTileOptions
 - olx.source.XYZOptions
 - olx.source.WMTSOptions
 - olx.source.ZoomifyOptions

src/ol/source/xyzsource.js

@@ -38,6 +38,7 @@ ol.source.XYZ = function(options) {
 
   goog.base(this, {
     attributions: options.attributions,
+    cacheSize: options.cacheSize,
     crossOrigin: options.crossOrigin,
     logo: options.logo,
     opaque: options.opaque,