Impemented macro generation of fitness functions, greatly reducing the need for a human programmer to set this up for each problem presented. Includes some (very simple) default fitness functions for number, string, and boolean functions.

Also added program-wrapping so a generated program can be easily made into a first-class function. (Note that this is purely within the GP implementation; the Didact environment will take advantage of this fact and further wrap with metadata, as with all functions).
Removing mistaken commit.