simuls rotation

Simulations with the solver ns3d.strat with rotation. It contains:

• fluidsim/util/scripts/turb_rotation_trandom_anisotropic.py: useful script to fix parameters;
• doc/examples/forcing_anisotropic_3d/rotation: scripts for simulations on clusters;
• Compute dimensionless numbers (Re, Re4, Ro);
• Option to remove geostrophic modes;
• Diagnostics for geostrophic modes (spatial_means, spectra, spatiotemporal_spectra);