added missing serial id

SwingUtilities/src/main/java/fr/soleil/lib/project/swing/text/DocumentNumber.java

@@ -21,6 +21,8 @@ package fr.soleil.lib.project.swing.text;
  */
 public class DocumentNumber extends AFilteredDocument {
 
+    private static final long serialVersionUID = 1031277852234184282L;
+
     private boolean allowNegativeValues = false;
     private boolean allowFloatValues = false;
     private boolean allowScientificValues = false;