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/Internal/Modelling/CommandParameterComparer.cs

@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+
+namespace Spectre.Console.Cli.Internal
+{
+    internal static class CommandParameterComparer
+    {
+        public static readonly ByBackingPropertyComparer ByBackingProperty = new ByBackingPropertyComparer();
+
+        public sealed class ByBackingPropertyComparer : IEqualityComparer<CommandParameter?>
+        {
+            public bool Equals(CommandParameter? x, CommandParameter? y)
+            {
+                if (x is null || y is null)
+                {
+                    return false;
+                }
+
+                if (ReferenceEquals(x, y))
+                {
+                    return true;
+                }
+
+                return x.Property.MetadataToken == y.Property.MetadataToken;
+            }
+
+            public int GetHashCode(CommandParameter? obj)
+            {
+                return obj?.Property?.MetadataToken.GetHashCode() ?? 0;
+            }
+        }
+    }
+}