HeaderResourceFactory provides HeaderResource instance to manage tags, such
as <link> and <script>, in <head> tag.
HeaderResourceFactory is defined by jetspeed-spring.xml. If you want to use
customized HeaderResource, the parameter needs to be changed in
jetspeed-spring.xml.
author: Shinsuke Sugaya version: $Id: PortalReservedParameters.java 188569 2005-05-13 13:35:18Z weaver $