Elwig: Rename buchführend, funktionär, volllieferant, and gebunden

Elwig/Models/Entities/DeliveryPart.cs

@@ -91,8 +91,8 @@ namespace Elwig.Models.Entities {
         [Column("hand_picked")]
         public bool? IsHandPicked { get; set; }
 
-        [Column("gebunden")]
-        public bool? IsGebunden { get; set; }
+        [Column("contracted")]
+        public bool? IsContracted { get; set; }
 
         [Column("unloading")]
         public string? Unloading { get; set; }