Adds mutation category based dreams when sleeping

The player will now get strange dreams during sleep when heavily mutated. The dreams will vary based upon the player's strongest category and the strength. More highly mutated players will get more intense dreams. The frequency of the dreams will also change based upon the strength of the category, a lightly mutated player may only get one dream every couple of nights, while a heavily mutated one may get several per night.

This also gives the player a way of determining the category they're leaning towards.

I've added a function to return the player's strongest mutation category, and another that gives the strength of a given category.

I've also added in two possible dreams for every level of every category, but that can be easily expanded.

I'll admit that I'm not the most creative person, so the dreams I've added aren't overly interesting or diverse, but they provide an adequate starting point.

Some of this stuff was new ground for me so I'm also quite open to suggestions on it.