Add some docs

src/main/java/ui/implementation/dialogs/GreyScalePicker.java

@@ -2,6 +2,9 @@ package ui.implementation.dialogs;
 
 import java.awt.Color;
 
+/**
+ * @author Laurent Crema, Jean-Marc Wagner
+ */
 public class GreyScalePicker extends javax.swing.JDialog
 {
     private int couleur;