Added placeholders for the Spanish source code files. Corrected/translated the first 3 scripts

I have corrected/translated the first 3 python scripts:

- hello.py->hola.py
- guess.py->adivinaElNúmero.py
- dragon.py->dragón.py

I have also added placeholders for Spanish code scripts (e.g. "es_collisionDetection.py") that will be removed as the translated files (e.g. "detecciónDeColisiones.py") are added.

I need to check with Al whether he intends to translate the names of the additional files (e.g. "cherry.jpg" -> "cereza.jpg")