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/CommandContext.cs

@@ -0,0 +1,45 @@
+namespace Spectre.Console.Cli
+{
+    /// <summary>
+    /// Represents a command context.
+    /// </summary>
+    public sealed class CommandContext
+    {
+        /// <summary>
+        /// Gets the remaining arguments.
+        /// </summary>
+        /// <value>
+        /// The remaining arguments.
+        /// </value>
+        public IRemainingArguments Remaining { get; }
+
+        /// <summary>
+        /// Gets the name of the command.
+        /// </summary>
+        /// <value>
+        /// The name of the command.
+        /// </value>
+        public string Name { get; }
+
+        /// <summary>
+        /// Gets the data that was passed to the command during registration (if any).
+        /// </summary>
+        /// <value>
+        /// The command data.
+        /// </value>
+        public object? Data { get; }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="CommandContext"/> class.
+        /// </summary>
+        /// <param name="remaining">The remaining arguments.</param>
+        /// <param name="name">The command name.</param>
+        /// <param name="data">The command data.</param>
+        public CommandContext(IRemainingArguments remaining, string name, object? data)
+        {
+            Remaining = remaining ?? throw new System.ArgumentNullException(nameof(remaining));
+            Name = name ?? throw new System.ArgumentNullException(nameof(name));
+            Data = data;
+        }
+    }
+}