Add support for the Xamarin.iOS Unified platform

[GoogleCodeExporter]

Is it possible to add the xamarinios1 platform to the NuGet NuSpec for the 
current stable release? 
And of course, the later versions. This would be great as we will be able to 
feature this library on the Xamarin Component Store.

The new entry would be:

lib\portable-net4+sl5+netcore45+wpa81+wp8+MonoAndroid1+MonoTouch1+XamariniOS1

I am not sure what I would need to do for this...

Original issue reported on code.google.com by matthew....@xamarin.com on 6 Feb 2015 at 1:26