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/ServiceConfiguration.cs

@@ -0,0 +1,7 @@
+namespace Ryujinx.HLE.HOS.Services
+{
+    public static class ServiceConfiguration
+    {
+        public static bool IgnoreMissingServices { get; set; }
+    }
+}