Make SelectionBean serializable

src/main/java/org/genesys2/server/servlet/controller/SelectionBean.java

@@ -16,6 +16,7 @@
 
 package org.genesys2.server.servlet.controller;
 
+import java.io.Serializable;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -25,7 +26,9 @@ import org.springframework.stereotype.Component;
 
 @Component
 @Scope("session")
-public class SelectionBean {
+public class SelectionBean implements Serializable {
+	private static final long serialVersionUID = -1084615112110837714L;
+
 	private Set<Long> accessionIds = new HashSet<Long>();
 
 	public Set<Long> getAccessionIds() {