IPC services refactoring (#726)

* IPC services refactoring

- Use custom Attributes to handle services.
- Add a way to set the permissions and fix the bsd service to use it.
- Little cleanup.
- C#7.1 is required.

* fix var name

* fix syntax

* Change Permission to Parameter

* Delete BsdServicePermissionLevel.cs

* Fix Linq

Ryujinx.HLE/HOS/Services/Aud/IAudioOutManager.cs

@@ -11,6 +11,7 @@ using static Ryujinx.HLE.HOS.ErrorCode;
 
 namespace Ryujinx.HLE.HOS.Services.Aud
 {
+    [Service("audout:u")]
     class IAudioOutManager : IpcService
     {
         private const string DefaultAudioOutput = "DeviceOut";
@@ -23,7 +24,7 @@ namespace Ryujinx.HLE.HOS.Services.Aud
 
         public override IReadOnlyDictionary<int, ServiceProcessRequest> Commands => _commands;
 
-        public IAudioOutManager()
+        public IAudioOutManager(ServiceCtx context)
         {
             _commands = new Dictionary<int, ServiceProcessRequest>
             {