Don't loop to integrate ρ. Also, remove duplicated ζ contribution to pressure.
Don't loop to integrate ρ. Also, remove duplicated ζ contribution to pressure.

The explicit free-surface term for pressure comes from the linearization.
Here, I just integrate ρ from surface to bottom.

dcherian/eddyshelf,dcherian/eddyshelf,dcherian/eddyshelf