Insert NuGet Build 4.6.0-preview2-4706 into sdk

[nugetlurker]

Insert NuGet Build 4.6.0-preview2-4706 into sdk master branch

[johnbeisner]

@tannergooding
Did you mention that you had a fix to the package error?

[tannergooding]

@johnbeisner, the remaining issues I know about should be resolved by #1804

[emgarten]

Rebasing on the latest master

[emgarten]

Looks like this is failing with
error NU1608: Detected package version outside of dependency constraint: Microsoft.Build.Tasks.Core 15.1.1012 requires Microsoft.Build.Framework (= 15.1.1012) but version Microsoft.Build.Framework 15.4.8 was resolved. [/Users/dotnet-bot/j/workspace/dotnet_sdk/master/debug_osx10.12_prtest/sdk.sln]

Is there an exact version of Microsoft.Build.Framework that NuGet should reference here? Or should this be NoWarned?

[johnbeisner]

@emgarten
We are going to need to resolve CLI first before addressing the SDK, SDK will take a reference to the CLI build with the new NuGet version.

[johnbeisner]

NuGet team is authoring a fix; reference: dotnet/cli#8200