Added local multiplayer/coop!!! (Beta)

I added local multiplayer/coop mode for you to enjoy this game with your friends!
It's still in beta testing mode, not finished, some stuff might not properly work, but you can already play with friends.
The first player is controlled by keyboard, the rest of the players are assigned to each next controller you have connected, to join you just need to press a button on a controller.
I said it's unfinished because you can't save the game in coop, yet, that will come in the near future, also some stuff might break while playing in coop.
For now, it's only local.
Have fun! Let me know your thoughts!