Update build.cmd to use latest nuget

[tushargupta51]

build.cmd downloads the nuget.exe from https://nuget.org/nuget.exe. That does not download the latest version. Use https://dist.nuget.org/win-x86-commandline/latest/nuget.exe instead.

Also, update nuget.config to use v3 feeds (both myget and nuget), they are faster than v2 feeds. KRelease branch has those changes: