[#43] PaymentVariantWindow: Do not use Context from ContextWindow any more

Elwig/Helpers/AppDbContext.cs

@@ -56,6 +56,7 @@ namespace Elwig.Helpers {
         public DbSet<DeliveryPartModifier> DeliveryPartModifiers { get; private set; }
         public DbSet<PaymentVar> PaymentVariants { get; private set; }
         public DbSet<PaymentMember> MemberPayments { get; private set; }
+        public DbSet<PaymentDeliveryPart> PaymentDeliveryParts { get; private set; }
         public DbSet<Credit> Credits { get; private set; }
 
         public DbSet<OverUnderDeliveryRow> OverUnderDeliveryRows { get; private set; }