Update v0.5.6 balance changes and difficulty changes

-Changed difficulty descriptions since the multiplier didn't faithfully portray the challenge each difficulty provides, and wrongly suggested that the player was having much difficulty at a level that was supposed to be easy.

For example I, who is the developer of the game with hundreds of hours of gameplay get a challenging experience on Nightmare difficulty which had a x1.0 modifier, which suggested it was akin to normal difficulty which is false.

Now, if you hover over a difficulty, it will show a tooltip with all that changes along with how much exp you earn.

-Boss Health now scales with the difficulty picked and slightly increases each Stage.

-Bosses now spawn further away from the Player the faster they are, so that they reach the Player at somewhat imilar timing.

-Enemies now level up slightly faster

-Enemies will now start shooting at the Player after they get even closer (x0.8 -> x0.7 of Weapon Range)

-Increased enemy code performance

-improved fighter AI.