Supporting local models

[DougBurke]

I want to be able to able support users who want to use XSPEC local models. The idea would be to provide functionality in this module to act like XSPECs initpackage and lmod commands (i.e. create a new module) rather than have then added to this module. I'm basing this in my create_xspec_user_model script in CIAO.

Things we may want

• access to the initialization routine from C++ scope
• access to the C++ template code that is used to create the function to wrap the model - that is both

template <xsccCall model, int NumPars>
py::array_t<Real> wrapper_C(py::array_t<Real> pars,
                            py::array_t<Real, py::array::c_style | py::array::forcecast> energyArray,
                            const int spectrumNumber,
                            const string initStr) {
...

and

    m.def("apec", wrapper_C<C_apec, 3>, "The XSPEC additive apec model (3 parameters).","pars"_a,"energies"_a,"spectrum"_a=1,"initStr"_a="");