Added new BeanCreationContext interface.

This interface encapsulates all information needed for the creation of a bean.
In addition, it provides a mechanism for the creation of nested beans (e.g.
constructor arguments or nested properties) which is not tight to
BeanHelper. This is required for changing the way BeanHelper is used in
future.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1520791 13f79535-47bb-0310-9956-ffa450edef68