Use original name for templated global function

[varunagrawal]

Fixes #148

[gchenfc]

Correct me if I'm wrong, but isn't this API breaking since every templated global function name will change?

Also, is it possible that this might cause more overload resolution issues with implicitly convertible types or types that generally are difficult for pybind/matlab to distinguish? e.g.

template <typename T = {double, int>
void function(const T& arg);

or

template <typename T = {std::vector<double>, gtsam::KeyVector>
void function(const T& arg);

?

[varunagrawal]

True it is API breaking, but it follows with the design @dellaert wants from #148.

As for the second point, that would be the case for the current version of the wrapper as well. double and int is not a good example since they correspond to float and int in python, but functionInt and functionSize_t would still have the same behavior. Plus we already have overloading like this working for the Values class in GTSAM.

[ProfFan]

Overload resolution is tricky and I think what Frank wants (based on our last talk) is we explicitly define these typed overloads in the .i files and leave most overloads automatically resolved. I don't fully agree but it is a reasonable plan.