Fix some issues with the new Resources implementation reported by Dan Mikusa:
- The zero-arg constructors for WebResourceSet implementations were either missing or always failed meaning that they could not be specified in a context.xml file as the digester was unable to create them
- The internalPath attribute was not configurable

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1520575 13f79535-47bb-0310-9956-ffa450edef68