Add Spectre.Cli to Spectre.Console

* Renames Spectre.Cli to Spectre.Console.Cli.
* Now uses Verify with Spectre.Console.Cli tests.
* Removes some duplicate definitions.

Closes #168

examples/Cli/Demo/Program.cs

@@ -0,0 +1,37 @@
+using Demo.Commands;
+using Spectre.Console.Cli;
+
+namespace Demo
+{
+    public static class Program
+    {
+        public static int Main(string[] args)
+        {
+            var app = new CommandApp();
+            app.Configure(config =>
+            {
+                config.SetApplicationName("fake-dotnet");
+                config.ValidateExamples();
+                config.AddExample(new[] { "run", "--no-build" });
+
+                // Run
+                config.AddCommand<RunCommand>("run");
+
+                // Add
+                config.AddBranch<AddSettings>("add", add =>
+                {
+                    add.SetDescription("Add a package or reference to a .NET project");
+                    add.AddCommand<AddPackageCommand>("package");
+                    add.AddCommand<AddReferenceCommand>("reference");
+                });
+
+                // Serve
+                config.AddCommand<ServeCommand>("serve")
+                    .WithExample(new[] { "serve", "-o", "firefox" })
+                    .WithExample(new[] { "serve", "--port", "80", "-o", "firefox" });
+            });
+
+            return app.Run(args);
+        }
+    }
+}