IDE-931 Support custom portlet categories in portlet wizard #resolve

extend the search mechanism of pulling categories to not only look in the current portlet project's custom categories in liferay-display.xml, but also in all the other portlet plugin projects' custom categories.
IDE-931

modified foundDuplicate variable's location in previous commit.
IDE-945 updated dtds and xsd for 6.2.0-M5 #resolve
IDE-932

Make sure the default superclasses show up when
creating custom portlet class during new liferay project