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/Dynamic/Program.cs

@@ -0,0 +1,24 @@
+using System.Linq;
+using Spectre.Console.Cli;
+
+namespace Dynamic
+{
+    public static class Program
+    {
+        public static int Main(string[] args)
+        {
+            var app = new CommandApp();
+            app.Configure(config =>
+            {
+                foreach(var index in Enumerable.Range(1, 10))
+                {
+                    config.AddCommand<MyCommand>($"c{index}")
+                        .WithDescription($"Prints the number {index}")
+                        .WithData(index);
+                }
+            });
+
+            return app.Run(args);
+        }
+    }
+}