test - experiment : ideal_2D_oce

purpose: Shows that the residual mean circulation is becoming small
 at the Equilibrium (Bolus cancel the Euleurian circ.) and is function
 of the diapycnal mixing.

Set up:
 Idealized 2D global ocean with flat bathymetry and no continent,
 symetric relative to the Eq.
 Forcing: zonal wind stress and surface temp. relaxation toward a
 "realistic" SST (function of Latitude).

To reduce diapycnal mixing, "exotic" parameters are used (and tested)
in this test-experiment:
a) vertical discretization: interface at the middle (use delRc)
b) GM advect form
c) use Visbeck
d) GM advect(Euler+Bolus) and Flux Limit Adv scheme.
e) 3 different time-steps (MOM,FS,Tracer)
f) oceanic exp using stagger time stepping
g) oceanic exp using cg2dTargetResWunit