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

src/Spectre.Console/Cli/ICommandParameterInfo.cs

@@ -0,0 +1,20 @@
+namespace Spectre.Console.Cli
+{
+    /// <summary>
+    /// Represents a command parameter.
+    /// </summary>
+    public interface ICommandParameterInfo
+    {
+        /// <summary>
+        /// Gets the property name.
+        /// </summary>
+        /// <value>The property name.</value>
+        public abstract string PropertyName { get; }
+
+        /// <summary>
+        /// Gets the description.
+        /// </summary>
+        /// <value>The description.</value>
+        public abstract string? Description { get; }
+    }
+}