refactor settings load/save

- load using LINUQ
- load on child settings on demond
- prevent error when plugin has been removed
- prevent settings loose when plugin has been removed

Pilz.Configuration/ISettings.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using Newtonsoft.Json;
+using System.Collections.Generic;
 
 namespace Pilz.Configuration;
 
@@ -7,4 +8,6 @@ public interface ISettings
     IReadOnlyCollection<IChildSettings> Childs { get; }
     T Get<T>() where T : IChildSettings, ISettingsIdentifier;
     void Reset();
+    string Save(JsonSerializerSettings serializer);
+    bool Load(JsonSerializerSettings serializer, string raw);
 }