PlaceParticlesOnIsopycnal

MAS 1/10/18 - added intext (‘int’ or ‘both’) to give option of using int vs. int+ext fields for rho_prime

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Discussion

Also added rhoIsopycnal as output. Any floats with the same value of z will be moved to the same isopycnal.

interpolation should probably be ‘spline’. tolerance is in meters, 1e-8 should be fine.