Refactor the build scripts

- Bifurcate Package and Publish targets to enable signing.
- Move publish from bash/ps into c#.
- Create multiple targets to create MSIs and Bundles.

scripts/dotnet-cli-build/Utils/Monikers.cs

@@ -0,0 +1,35 @@
+using Microsoft.DotNet.Cli.Build.Framework;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Microsoft.DotNet.Cli.Build
+{
+    public class Monikers
+    {
+        public static string GetProductMoniker(BuildTargetContext c)
+        {
+            string osname = GetOSShortName();
+            var arch = CurrentArchitecture.Current.ToString();
+            var version = c.BuildContext.Get<BuildVersion>("BuildVersion").SimpleVersion;
+            return $"dotnet-{osname}-{arch}.{version}";
+        }
+
+        public static string GetOSShortName()
+        {
+            string osname = "";
+            switch (CurrentPlatform.Current)
+            {
+                case BuildPlatform.Windows:
+                    osname = "win";
+                    break;
+                default:
+                    osname = CurrentPlatform.Current.ToString().ToLower();
+                    break;
+            }
+
+            return osname;
+        }
+    }
+}