Removed direct dependency to PropertyConverter.

Data type conversions are now performed by a ConversionHandler object. The
ConversionHandler instance to be used can be passed to the constructor of
DefaultBeanFactory. Alternatively, a default instance is used.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1516575 13f79535-47bb-0310-9956-ffa450edef68