Changes in MBF 5.50:
-------------------

MBF was updated according to the changes in QMBF 5.50:

- new option for uncorrelated fits: Inversion method "Diagonal only"

- four new "upper" matrix models for triangular matrix fits (= symmetrized matrix fits; see user manual for details)

- improved performance of the "Additional term in chi^2" option (compute derivatives only for relevant parameters)