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/Commands/Add/AddReferenceCommand.cs

@@ -0,0 +1,30 @@
+using System.ComponentModel;
+using Demo.Utilities;
+using Spectre.Console.Cli;
+
+namespace Demo.Commands
+{
+    public sealed class AddReferenceCommand : Command<AddReferenceCommand.Settings>
+    {
+        public sealed class Settings : AddSettings
+        {
+            [CommandArgument(0, "<PROJECTPATH>")]
+            [Description("The package reference to add.")]
+            public string ProjectPath { get; set; }
+
+            [CommandOption("-f|--framework <FRAMEWORK>")]
+            [Description("Add the reference only when targeting a specific framework.")]
+            public string Framework { get; set; }
+
+            [CommandOption("--interactive")]
+            [Description("Allows the command to stop and wait for user input or action (for example to complete authentication).")]
+            public bool Interactive { get; set; }
+        }
+
+        public override int Execute(CommandContext context, Settings settings)
+        {
+            SettingsDumper.Dump(settings);
+            return 0;
+        }
+    }
+}