Parse a configuration file and build the XML tree below the given parent node (or
null if not given). Only the nodes corresponding to the classes in
includedClasses and their parent nodes are created. Other nodes in the XML tree are ignored.
This method is the same as parseConfigFile(fileName, includedClasses, true).
@param fileName The name of the configuration file.
@param includedClasses The set of names of classes to be included.
@exception Exception If error occurs.
@see #parseConfigFile(String,Set,boolean)