Google and Yandex tile-layers changed

1. An event "MapObjectInitialized" (with map-object as its argument)
added to "_initMapObject" of Google and Yandex layers, so the code that
uses plug-ins will be able to use their JS API through their
map-objects.
2. Yandex map type initialization changed (see explanation in comments)
3. Yandex map-object creation completed (see explanation in comments)