Multi Project Validator

A tool which searches recursively for project.json files,
runs a set of analyses and reports on the result.

For CLI we have only one rule currently, that Dependencies
between projects must be equivalent to avoid stomping.

src/Microsoft.DotNet.Cli.Utils/Constants.cs

@@ -11,6 +11,7 @@ namespace Microsoft.DotNet.Cli.Utils
 {
     internal static class Constants
     {
+        public static readonly string ProjectFileName = "project.json";
         public static readonly string ExeSuffix = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? ".exe" : string.Empty;
 
         // Priority order of runnable suffixes to look for and run