Common Props file to bypass Package Warning

As of VS2015.3 & a recent .NET Core & MSBuild revisions, a breaking build change was introduced to make NU1605 a build breaking warning by default.
This causes hundreds of build errors in the project due to the presence of newer framework and .net core library versions.
This common props file ignores the warning.

See: NuGet/Home#5594

Author: Eoin Campbell

src/Directory.Build.props

@@ -0,0 +1,5 @@
+<Project>
+  <PropertyGroup>
+    <NoWarn>$(NoWarn);NU1605</NoWarn>
+  </PropertyGroup>
+</Project>