Changes

Now that the value of wp3 is being set to a boundary value of 0
at the first thermodynamic grid level above the surface, it doesn't
make sense to loop over budget terms anymore at that particular level,
since they don't factor in the solution and give a false impression.

With this commit, wp3 budget terms now start their loop at level 3.

This commit is BIT_CHANGING, but the only thing that changes are
budget stats for a couple of wp3 budget terms. The solution
does not actually change.