Updated user's guide related to changes on BeanHelper.

Since BeanHelper is no longer a static utility class, its usage patterns have
changed. This has to be reflected in the examples and descriptions provided by
the user's guide.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1520799 13f79535-47bb-0310-9956-ffa450edef68