Add Jacobian to GeneralizedLorentz1D, SmoothBrokenPowerLaw in stingray.simulator.models

[ankitkhushwaha]

TODO:

i have added the jacabian for each parameter in both GeneralizedLorentz1D, SmoothBrokenPowerLaw function.

i have confirmed that jacobian for function with respect to each parameter is correct.

@matteobachetti

[ankitkhushwaha]

I think changes are ready for review.
@matteobachetti

[matteobachetti]

@ankitkhushwaha thanks for your PR. However, I haven't noticed any tests failing, there are no issues open about it as far as I can tell. Could you be clearer about what is failing, and what your changes do?

[ankitkhushwaha]

@matteobachetti
in the first commit. Function GeneralizedLorentz1D, SmoothBrokenPowerLaw was returning the jacobian and function output as tuple. that's why some test are falling.

these test are fixed now.

TODO:
I have added the Jacobian functionality for GeneralizedLorentz1D, SmoothBrokenPowerLaw which will compute the derivative of their function with respective to each parameter.