Feature #2: Implement Repair Provider

Logging Repair for Non-Warranty jobs has been brought into line with
Logging Warranty. RepairProviderFeature implemented which allows plugins
to be used in submitting jobs to third-parties for repair.

Disco.Models/Repository/Device/DeviceModel.cs

@@ -33,6 +33,9 @@ namespace Disco.Models.Repository
         [StringLength(40)]
         public string DefaultWarrantyProvider { get; set; }
 
+        [StringLength(40)]
+        public string DefaultRepairProvider { get; set; }
+
         public virtual IList<DeviceComponent> DeviceComponents { get; set; }
 
         public virtual IList<Device> Devices { get; set; }