Project.json restore should warn when top level packages violate constraints

[emgarten]

The below project.json should generate a warning for the constraint violation between Microsoft.ApplicationInsights >= 2.0.0 and == 1.2.3 required by the WindowsApp package.

Ideally there should also be a way to suppress these warnings.

{
  "dependencies": {
    "Microsoft.ApplicationInsights": "2.0.0",
    "Microsoft.ApplicationInsights.PersistenceChannel": "1.2.3",
    "Microsoft.ApplicationInsights.WindowsApps": "1.1.1",
    "Microsoft.NETCore.UniversalWindowsPlatform": "5.0.0",
    "Win2D.uwp": "1.16.0"
  },
  "frameworks": {
    "uap10.0": {}
  },
  "runtimes": {
    "win10-arm": {},
    "win10-arm-aot": {},
    "win10-x86": {},
    "win10-x86-aot": {},
    "win10-x64": {},
    "win10-x64-aot": {}
  }
}

[lindydonna]

@emgarten Shouldn't it be more than a warning? In previous versions of NuGet, it would be an error.