Feature #25: Job General Preferences

Initially to make 'long running job threshold' configurable. Updates to
ManagedJobList and fix for missing GetClaimKeys method (#24).

Disco.Models/UI/Config/JobPreferences/ConfigJobPreferencesIndexModel.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Disco.Models.UI.Config.JobPreferences
+{
+    public interface ConfigJobPreferencesIndexModel : BaseUIModel
+    {
+        int LongRunningJobDaysThreshold { get; set; }
+
+        List<KeyValuePair<int, string>> LongRunningJobDaysThresholdOptions();
+    }
+}