What even is a heruistic?

Todo: investigate why [(x) / 2] + [(x - 12) / 3 + 47] = [ ] + [(-21) /
2] has such a low heruistic.  The first term isn't getting penalized for
having to multiply on the second term.
Fixed some late night OBOEs
Prune out noop drags
Dependent Terms don't care about block holders

Also, unseen here, but I was testing on an unsolvable equation.  AGH
Normalized dealing with numberblocks

And discouraged having large number chains (a small tweak to be more
human like)
penalized unnecessary drags and encouraged dividing out

This seems to solve difficulty 2 problems pretty well.
Documented heuristic v0.2

This should be good enough for a start.  It can solve 1000 level 2
problems in under 80 seconds.  I think a more clever approach will be
needed for level 3 and 4.