Added a new system test for the prolate diffusion tensor, this time checking the diffusion type.
A spherical tensor is sent in, triggering the bug found by Vitaly Vostri <vvostri att gmail dott
com> (Message-id: <AANLkTinRO3ZCNwL6GeqWdx0uBvv=PQ=zw6vpdQQeruBW@...>
https://mail.gna.org/public/relax-users/2010-12/msg00014.html).
The problem is that the prolate tensor is changed to an oblate one!?!
