Doc: Edit docs for the Connections view

- You have to double-click the values of columns to edit them
- For properties and bindings, the values are set for the currently
  selected item and the item column displays the item id (read-only)
- Add links to examples of using the view

Change-Id: I8c27dbbcbbf269f52102ca2af37f872c86e56155
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

doc/src/qtquick/qtquick-connection-editor.qdoc

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2018 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the Qt Creator documentation.
@@ -70,4 +70,7 @@
         \li \l{Managing C++ Backend Objects}
         \endif
     \endlist
+
+    For an example of using properties, bindings, and connections to create a
+    scalable push button, see \l{Creating Scalable Buttons and Borders}.
 */