I have just updated all my nuget packages for my solution (dotnet core 1.1 project).
I am now getting the following warnings and I don\'t really know what they mean.
I was able to get rid of these warnings in my project by removing the element from the csproj file.
There's some information in this article about implicit metapackages, which seems to be the root cause of this problem.
You might also need to update some dependencies. For example, I had to upgrade BenchmarkDotNet from 0.10.1 to 0.10.3 to get rid of a few warnings like the ones you're seeing.