Use pybind functionality enabled by c++14

[mormj]

Since our pybind11 integrations were developed when master was still on c++11, we missed out on some of the syntactical niceties such as:

https://pybind11.readthedocs.io/en/stable/classes.html?highlight=overloaded#overloaded-methods

where

py::class_<Pet>(m, "Pet")
   .def(py::init<const std::string &, int>())
   .def("set", static_cast<void (Pet::*)(int)>(&Pet::set), "Set the pet's age")
   .def("set", static_cast<void (Pet::*)(const std::string &)>(&Pet::set), "Set the pet's name");

becomes

py::class_<Pet>(m, "Pet")
    .def("set", py::overload_cast<int>(&Pet::set), "Set the pet's age")
    .def("set", py::overload_cast<const std::string &>(&Pet::set), "Set the pet's name");

This can be done in the in-tree bindings, but more importantly should be updated in the modtool template and bindtool

[marcusmueller]

we're doing this here and there in the tree right now! ❤️

I don't think we'll spend energy on converting the existing codebase to do it everywhere, though.