Implemented command type readers, parser and service.

src/Discord.Net.Commands/CommandError.cs

@@ -0,0 +1,20 @@
+namespace Discord.Commands
+{
+    public enum CommandError
+    {
+        //Search
+        UnknownCommand,
+
+        //Parse
+        ParseFailed,
+        BadArgCount,
+
+        //Parse (Type Reader)
+        CastFailed,
+        ObjectNotFound,
+        MultipleMatches,
+
+        //Execute
+        Exception,
+    }
+}