Optimizing resource management

This week I did some work on externalizing a lot of hard-coded stuff for sprites, sound effects and spells parameters. This will make it easier in the future development to create and use other sprites. Mostly it will prevent to recompile all the code to move a button 2 pixels to the left which is a huge waste of time.

This allowed me to implement lots of small animation for the "spells" the players cast.