Fix @since for 7.4

Change-Id: I71f3a7cd6b91174c306e5cd60e20dbf0150f4a53

client/src/com/vaadin/client/ApplicationConnection.java

      * might be in an inconsistent state because some state changes have been
      * applied but others not. This includes running layotus.
      * 
-     * @since 
+     * @since 7.4
      * @return <code>true</code> if the internal state might be inconsistent
      *         because changes are being processed; <code>false</code> if the
      *         state should be consistent

client/src/com/vaadin/client/widget/grid/events/BodyDoubleClickHandler.java

  * Handler for {@link GridDoubleClickEvent}s that happen in the body of the
  * Grid.
  * 
- * @since
+ * @since 7.4
  * @author Vaadin Ltd
  */
 public interface BodyDoubleClickHandler extends GridDoubleClickHandler {

client/src/com/vaadin/client/widget/grid/events/FooterDoubleClickHandler.java

  * Handler for {@link GridDoubleClickEvent}s that happen in the footer of the
  * Grid.
  * 
- * @since
+ * @since 7.4
  * @author Vaadin Ltd
  */
 public interface FooterDoubleClickHandler extends GridDoubleClickHandler {

client/src/com/vaadin/client/widget/grid/events/GridDoubleClickEvent.java

 /**
  * Represents native mouse double click event in Grid.
  * 
- * @since
+ * @since 7.4
  * @author Vaadin Ltd
  */
 public class GridDoubleClickEvent extends

client/src/com/vaadin/client/widget/grid/events/HeaderDoubleClickHandler.java

  * Handler for {@link GridDoubleClickEvent}s that happen in the header of the
  * Grid.
  * 
- * @since
+ * @since 7.4
  * @author Vaadin Ltd
  */
 public interface HeaderDoubleClickHandler extends GridDoubleClickHandler {

server/src/com/vaadin/server/JsonCodec.java

      * {@link JsonValue#jsEquals(JsonValue)} is defined to use JavaScript
      * semantics where arrays and objects are equals only based on identity.
      * 
-     * @since
+     * @since 7.4
      * @param a
      *            the first json value to check, may not be null
      * @param b