introduce the concept of system contributions

EDPlayerJournal/BGS/MissionCompleted.cs

@@ -40,6 +40,23 @@ public class MissionCompleted : Transaction {
         }
     }
 
+    /// <summary>
+    /// Rescue missions contribute to the system.
+    /// </summary>
+    public override bool SystemContribution {
+        get {
+            if (AcceptedEntry == null || AcceptedEntry.Mission == null) {
+                return false;
+            }
+
+            if (AcceptedEntry.Mission.IsRescueMission) {
+                return true;
+            }
+
+            return false;
+        }
+    }
+
     public override string ToString() {
         if (Faction == null || CompletedEntry == null || CompletedEntry.Mission == null) {
             return "";

EDPlayerJournal/BGS/Transaction.cs

@@ -21,6 +21,16 @@ public class Transaction : IComparable<Transaction> {
         }
     }
 
+    /// <summary>
+    /// Whether the transaction helps the entire system.
+    /// While all transactions are related to one faction, sometimes their
+    /// overall effect on the system as a whole is more important, than to
+    /// their faction. For example, rescuing refugees helps the Thargoid war
+    /// effort in the system as a whole, not just for the faction.
+    /// So this is true for transactions that help the system as a whole.
+    /// </summary>
+    public virtual bool SystemContribution { get; } = false;
+
     /// <summary>
     /// Returns true if this transaction was completed in legacy ED
     /// </summary>