Move Site Extension to nuget.org

[davidebbo]

Please see Azure/app-service-announcements#87 for detailed announcement.

Important: if your site extension is still relevant, you need to do this before June 1st 2018. Please let me know if you have any questions.

Thanks!

[rfcdejong]

Awaiting feedback from Toby

[rfcdejong]

Created a pull request #6

@toby-meyer I pushed it to nuget and I want to add you as an owner, but it cannot find you?