Merging JacobiElliptic with SpecialFunctions

I'm the current maintainer of [JacobiElliptic](https://github.com/dominic-chang/JacobiElliptic.jl). Your project was brought to my attention recently, and I was thinking that it would be better for the community for me to merge my implementations of the Elliptic integral functions and their inverses into `SpecialFunctions`. I notice that you have implementations of the some of the Fukushima set of algorithms. I have already implemented the remainder of the complete and incomplete Jacobi Integral functions, which I'm happy migrate into this code base and remove from my own.