Update .exe's project.json Target Framework from dnxcore50 to netstandardapp1.5.
Update .dll's project.json Target Framework from dnxcore50 to netstandard1.3.
Adding workaround for DataContractSerialization to src\dotnet\project.json to fix crossgen issue.
Build 23901 has a dependency issue that doesn't allow the runtime.any.System.Private.DataContractSerialization
package to be restored. When we move to a new build of CoreFX we should take this workaround out.
We have a bunch of NuGet.Config files in our tests that were needed before because the tests were run out of a temp directory. Now the tests are run out of the artifacts folder, which is a subdirectory of our repo root, so the root NuGet.Config will get picked up.
I also updated all the dotnet-core feeds from www.myget.org to dotnet.myget.org.
