Imported rule sets are those rulesets that are locatable within the current classpath but
are not part of standard PMD rule sets. To use this, you have to supply the rule set file name
(as opposed to the rule set name). All rule set files must be located in a hierarchy rulesets/[file name].
Rule set files are xml files. This property page allows you to simply type in the file name without the path
without the XML extension. It will then search the classpath for a file name of the form "rulesets/[filename].xml.
If found, it will import the rule set and make it available in the active rule set panel and the configure rule set
panel.