Update Windows build documentation for Win10/MPI
The Windows build documentation references older versions of Visual Studio, e.g. 2012, 2013, and use of a version of Boost binaries that won't work straightforwardly with recent VS versions. More generally, the build instructions are out of date for more recent versions of Visual Studio. Work is being done to resolve build issues and also add MPI support for Windows builds and the documentation needs updating to support this.