Automatically pick up !mutation

[Terrapin]

Now that mutation potions are actually useful in trunk, it would be nice to have autopickup automatically set to pick them up after identification. This obviously isn't a big deal, but I don't like to have to change the autopickup settings, and other good potions are automatically picked up.

[Elitist]

Mutations are still questionable and not strictly good, though I admit after using the first one (or being mutated otherwise) they almost become crucial to keep around, in the same way cure mutation used to be.