Synopsis
		sfcurvature < hor.rsf > cur.rsf rotation=n scale=1.0 vscale=1.0 what=

Parameters
		bool rotation=n [y/n] if y: rotation, if n: convergence   float scale=1.0 scaling (from time to depth)   float vscale=1.0 scaling (from time to depth)   string what= what to compute