fix npe, clear sbsv2 query cache data in memory when rebuilding sbsv2 cache from pref, other code clean-up
<?xml version="1.0" encoding="UTF-8"?>
<?eclipse version="3.2"?>
<plugin>
<extension-point id="featureUseTracker" name="Feature Usage Tracker" schema="schema/featureUseTracker.exsd"/>
</plugin>