Extend OS support to NanoServer

[ebekker]

This is extracted out from this comment by @thedevopsmachine:

Try replacing your "frameworks" entry in your project.json file with the following. It will allow you to extend your OS support to NanoServer.

"frameworks": {
    "netstandard1.6": {
      "dependencies": {
        "Microsoft.PowerShell.NanoServer.NetCore.Library": "1.0.0"
      }
    },
    "net452": {
      "dependencies": {
        "Microsoft.PowerShell.5.ReferenceAssemblies": "1.0.0"
      }
    }
  }