pokemon_battle.py - new Trainer class, new functions, documentation, fix of a bug and fix of some typos.

[Karaou-Mike]

• fixed a bug for wrong input when selecting a Pokemon's move
• added a pokemon_fight function in global scope
• added a Trainer class
• added a trainer_battle function in global scope
• fixed some typos
• added comments for better documentation

• removed fight function from Pokemon class

Now, you can create Pokemon trainers and create battles between them!