Converted Túbal Martín's Spherical Geometry PHP Class into .NET

Original PHP Code and Copyright is there http://tubalmartin.github.io/spherical-geometry-php/

Test results look same (This C# Version and PHP Version have good agreement) However, it doesn't look same as what google Map / Earth does. Especially if you have dent or crossover in the polygon. Don't assume it's perfect.

By the way, I did this in Xamarin, and I'm not sure if you can open in Visual Studio thing