BoV: Components/Button,CheckBox: Listener API updates

Change-Id: I266bf780d24e411b17d449ff5f9ce880fad53d36

documentation/components/components-button.asciidoc

 
 The [classname]#Button# component is normally used for initiating some action,
 such as finalizing input in forms. When the user clicks a button, a
-[classname]#Button.ClickEvent# is fired, which can be handled with a
-[interfacename]#Button.ClickListener# in the [methodname]#buttonClick()# method.
+[classname]#Button.ClickEvent# is fired, which can be handled by adding a __click listener__
+using either the [methodname]#onClick()# or the [methodname]#addClickListener()# method.
 
 You can handle button clicks with an anonymous class as follows:
 
 ----
 Button button = new Button("Do not press this button");
 
-button.addClickListener(new Button.ClickListener() {
-    public void buttonClick(ClickEvent event) {
-        Notification.show("Do not press this button again");
-    }
-});
-
-// Java 8
-button.addClickListener(click ->
+button.addClickListener(clickEvent ->
     Notification.show("Do not press this button again"));
 ----
 See the http://demo.vaadin.com/book-examples-vaadin7/book#component.button.basic[on-line example, window="_blank"].
 .Button in Different Styles of Valo Theme
 image::img/button-example1.png[width=70%, scaledwidth=100%]
 
-If you handle several buttons in the same listener, you can differentiate
-between them either by comparing the [classname]#Button# object reference
-returned by the [methodname]#getButton()# method of
-[classname]#Button.ClickEvent# to a kept reference. For a detailed description
-of these patterns together with some examples, please see
+If you handle several buttons in the same listener, you can differentiate between
+them by comparing the [classname]#Button# object reference returned by the [methodname]#getButton()#
+method of [classname]#Button.ClickEvent# to a kept reference. For a detailed description 
+of these patterns together with some examples, please see 
 <<dummy/../../../framework/architecture/architecture-events#architecture.events,"Events and Listeners">>.
 
 == CSS Style Rules

documentation/components/components-checkbox.asciidoc

 selection mode, as described in
 <<dummy/../../../framework/components/components-optiongroup#components.optiongroup,"OptionGroup">>.
 
-Clicking on a check box will change its state. The state is a
-[classname]#Boolean# property that you can set with the [methodname]#setValue()#
-method and obtain with the [methodname]#getValue()# method of the
-[classname]#Property# interface. Changing the value of a check box will cause a
-[classname]#ValueChangeEvent#, which can be handled by a
-[classname]#ValueChangeListener#.
+Clicking on a check box will change its state. The state is a [classname]#Boolean#
+property that you can set with the [methodname]#setValue()# method and obtain with
+the [methodname]#getValue()# method. Changing the value of a check box will cause
+a [classname]#ValueChangeEvent#, which can be handled by a [classname]#ValueChangeListener#.
 
 
 [source, java]
 
 checkbox2.setValue(true);
 
-checkbox1.addValueChangeListener(event -> // Java 8
+checkbox1.addValueChangeListener(event ->
     checkbox2.setValue(! checkbox1.getValue()));
 
-checkbox2.addValueChangeListener(event -> // Java 8
+checkbox2.addValueChangeListener(event ->
     checkbox1.setValue(! checkbox2.getValue()));
 ----