Add nuget packages

These are now live

One RxSpy only package at https://www.nuget.org/packages/RxSpy
And one RxSpy bundled with LiveView https://www.nuget.org/packages/RxSpy.LiveView

The RxSpy.LiveView package will install the liveview ui to the tools directory of the packages folder (thanks @paulcbetts) and RxSpy will automagically try to locate the tool from there. This is the easiest way to try RxSpy out.