l2 norm output

pressure error 1d: 0.0442536
pressure error 2d: 0.0536549
pressure error 3d: 0
velocity error 1d: 1.32782
velocity error 2d: 5.28391
velocity error 3d: 0
masked velocity error 2d: 2.34856
div error 1d: 1.41421
div error 2d: 2
div error 3d: 0
