changed a docstring and removed unused module
added a helper to get the ambient flow field
ambient flow doesnt use callback anymore as the statewriter uses a CG 1 function space, we need CG 2 to later calculate derivatives
approx shallow water wake model causes wake upstream - update is_in_wake to reflect that
added options to compute_gradient, defaults to True but not necessary for a genetic algorithm
changed mesh for approx shallow water model