Changes

Numerous bugs in the old [http://www.nmr-relax.com/api/1.0/maths_fns.correlation_time-module.html correlation time], [http://www.nmr-relax.com/api/1.0/maths_fns.weights-module.html weights], and [http://www.nmr-relax.com/api/1.0/maths_fns.direction_cosine-module.html direction cosine ] code have been fixed. A few of these bugs had been fixed previously but those fixes were somehow lost. Two major problems in the calculation of the Hessian of the ellipsoid direction cosines have been fixed and the ellipsoid diffusion tensor now minimises orders of magnitude faster.