Autoapply new default JS/CSS library preferences

Preferences JBossTools->Web->JS/CSS are initially set to default versions declared in extension point org.jboss.tools.jst.web.ui.jscssLibs. User can change some of them and leave some default libraries. New version of JBossTools may change some default libraries and add new.

With current implementation, user would have to go to preferences and use 'Restore Defaults' to get new default libraries. That is not good, new default libraries should replace old default libraries automatically.