[BEANUTILS-425] Externalized introspection mechanism.

A new BeanIntrospector interface was added. Implementations are now responsible
for obtaining property descriptors. This makes it possible to support bean
properties that are not compliant to the Java Beans specification.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/beanutils/trunk@1540350 13f79535-47bb-0310-9956-ffa450edef68
Updated changes.xml for [BEANUTILS-425].

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/beanutils/trunk@1540352 13f79535-47bb-0310-9956-ffa450edef68