Add a helper method to test if an instance of SumChargedEffort is zero.

FEA: ItEr75S27PerProjectDashboard

libreplan-business/src/main/java/org/libreplan/business/orders/entities/SumChargedEffort.java

@@ -70,4 +70,8 @@ public class SumChargedEffort extends BaseEntity {
         return directChargedEffort.plus(indirectChargedEffort);
     }
 
+    public boolean isZero() {
+        return directChargedEffort.isZero() && indirectChargedEffort.isZero();
+    }
+
 }