Use XML catalogs to point to some of our external schemas and what not

E.g. http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd for web.xml

These can be loaded from javax.servlet.resources in the servlet jar

Should help reduce some of the flakiness in the tests.

https://www.eclipse.org/webtools/wst/components/xml/M5/new_and_noteworthy/catalogContributions.html