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/Delegates/BarSettings.cs

@@ -0,0 +1,16 @@
+using System.ComponentModel;
+using Spectre.Console.Cli;
+
+namespace Delegates
+{
+    public static partial class Program
+    {
+        public sealed class BarSettings : CommandSettings
+        {
+            [CommandOption("--count")]
+            [Description("The number of bars to print")]
+            [DefaultValue(1)]
+            public int Count { get; set; }
+        }
+    }
+}