Tile renderers needn't listen for tile change

With this change the tile layer renderers no longer listen to tile changes. They just give tiles to load to the tile queue and wait for the tile queue/map to wake them up (`renderFrame_` calls) when new tiles have come in. This simplifies the code ("20 additions and 30 deletions"), and fixes a [bug](https://github.com/openlayers/ol3/pull/357#issuecomment-14900406) where the tile queue may have tiles to load but no one to trigger the load action.