Medusa System Added

Read about the medusa system [here](https://nadekobot.readthedocs.io/en/latest/medusa/creating-a-medusa/)

src/NadekoBot/Modules/Utility/CommandMap/CommandMapService.cs

@@ -52,7 +52,7 @@ public class CommandMapService : IInputTransformer, INService
         string input)
     {
         if (guild is null || string.IsNullOrWhiteSpace(input))
-            return input;
+            return null;
 
         if (AliasMaps.TryGetValue(guild.Id, out var maps))
         {
@@ -86,6 +86,6 @@ public class CommandMapService : IInputTransformer, INService
             }
         }
 
-        return input;
+        return null;
     }
 }

src/NadekoBot/Modules/Utility/ConfigCommands.cs

@@ -8,7 +8,7 @@ public partial class Utility
         private readonly IEnumerable<IConfigService> _settingServices;
 
         public ConfigCommands(IEnumerable<IConfigService> settingServices)
-            => _settingServices = settingServices;
+            => _settingServices = settingServices.Where(x => x.Name != "medusa");
 
         [Cmd]
         [OwnerOnly]