Remove TileEntry::isReady() and use bool(tile) directly
Remove TileEntry::isReady() and use bool(tile) directly

- avoid confusion with whether TileTask is ready
- other option rename isReady to hasTileReadyForRendering

tangrams/tangram-es,tangrams/tangram-es,tangrams/tangram-es,tangrams/tangram-es,tangrams/tangram-es,tangrams/tangram-es,tangrams/tangram-es