Power up spritekit particles

1. Add spritekit particle emitter effect for explosion. The explosion scene is presented on gameviewcontroller because it has a larger area for explosion view. Once the circuit is shorted, explosion view will be presented
2. Add bomb feature to beta. Once bomb is connected, the explosion scene will be presented too
Note: currently I'm exploding a spark image. I'll explode the real component image (like battery) in the future

Level 4 is modified for bomb and explosion test