Add missing @since values

Change-Id: I602b9fc4c87a19a78f949a23519c412aba789baa

client/src/com/vaadin/client/HasChildMeasurementHintConnector.java

  * Connector with layout measuring hint. Used to improve granularity of control
  * over child component measurements.
  * 
- * @since
+ * @since 7.6
  * @author Vaadin Ltd
  */
 public interface HasChildMeasurementHintConnector extends

client/src/com/vaadin/client/WidgetUtil.java

     /**
      * JavaScript hack to prevent text selection in various browsers.
      * 
-     * @since
+     * @since 7.6
      * @param e
      *            element for enabling or disabling text selection
      * @param enable

client/src/com/vaadin/client/communication/MessageHandler.java

             /**
              * Updates the hierarchy for a connector
              * 
-             * @since
              * @param connectorId
              *            the id of the connector to update
              * @param childConnectorIds

server/src/com/vaadin/ui/Calendar.java

      * Allow setting first day of week depending on Locale. Set to null if you
      * want first day of week depend on locale
      * 
-     * @since
+     * @since 7.6
      * @param dayOfWeek
      */
     public void setFirstDayOfWeek(Integer dayOfWeek) {

server/src/com/vaadin/ui/HasChildMeasurementHint.java

  * Component with layout measuring hint. Used to improve granularity of control
  * over child component measurements.
  * 
- * @since
+ * @since 7.6
  * @author Vaadin Ltd
  */
 public interface HasChildMeasurementHint extends HasComponents {