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/Psm/IPsmServer.cs

@@ -4,6 +4,7 @@ using System.Collections.Generic;
 
 namespace Ryujinx.HLE.HOS.Services.Psm
 {
+    [Service("psm")]
     class IPsmServer : IpcService
     {
         enum ChargerType
@@ -17,7 +18,7 @@ namespace Ryujinx.HLE.HOS.Services.Psm
 
         public override IReadOnlyDictionary<int, ServiceProcessRequest> Commands => _commands;
 
-        public IPsmServer()
+        public IPsmServer(ServiceCtx context)
         {
             _commands = new Dictionary<int, ServiceProcessRequest>
             {