supportsTile method
Returns true if MapDatabase contains the given tile.
@param tile tile to be rendered. @return true if tile is part of database.
Implementation
@override
Future<bool> supportsTile(Tile tile) async {
await _lateOpen();
if (!zoomlevelRange.matches(tile.zoomLevel)) return false;
return tile.getBoundingBox().intersects(getMapHeaderInfo().boundingBox);
}