Add Echo sample command

Author: ethanhann

src/InEngine.Commands/InEngine.Commands.csproj

@@ -42,6 +42,7 @@
     <Compile Include="..\SharedAssemblyInfo.cs">
       <Link>Properties\SharedAssemblyInfo.cs</Link>
     </Compile>
+    <Compile Include="Sample\Echo.cs" />
   </ItemGroup>
   <ItemGroup>
     <Folder Include="Sample\" />

src/InEngine.Commands/Options.cs

@@ -10,6 +10,9 @@ public class Options : IOptions
         [VerbOption("sample:minimal")]
         public Minimal Minimal { get; set; }
 
+        [VerbOption("sample:echo")]
+        public Echo Echo { get; set; }
+
         [HelpVerbOption]
         public string GetUsage(string verb)
         {

src/InEngine.Commands/Sample/Echo.cs

@@ -0,0 +1,18 @@
+using InEngine.Core;
+using System;
+using CommandLine;
+
+namespace InEngine.Commands.Sample
+{
+    public class Echo : AbstractCommand
+    {
+        [Option("text")]
+        public string Text { get; set; }
+
+        public override CommandResult Run()
+        {
+            Console.WriteLine(Text);
+            return new CommandResult(true);
+        }
+    }
+}