Adds setEmployees method

src/main/java/dgpena/siexample/persistence/Project.java

 package dgpena.siexample.persistence;
 
+import java.util.Collection;
 import java.util.Date;
 import java.util.HashSet;
 import java.util.Set;
@@ -45,6 +46,22 @@ public class Project {
 		return employees;
 	}
 	
+	public void setEmployees(Collection<Employee> employees) {
+		// remove my employees that are not in the new list of employees
+		for (Employee e: this.getEmployees()) {
+			if (!employees.contains(e)) {
+				this.removeEmployee(e);
+			}
+		}
+		
+		// add all the new employees
+		for (Employee e: employees) {
+			if (!this.getEmployees().contains(e)) {
+				this.addEmployee(e, new Date());
+			}
+		}
+	}
+
 	public void addEmployee(Employee e, Date startDate) {
 
 		ProjectAssignment pa = new ProjectAssignment();