Added function to target function to chi2, to try to compute the derivative of the chi2 function.
The function is in a test state, with several tests and looping.
task #7824(https://gna.org/task/index.php?7824): Model parameter ERROR estimation from Jacobian and Co-variance matrix of dispersion models.
Authored by: tlinnet 2014-09-02
Parent: [r25541]
Child: [r25543]
