SSO authentication module - RemoteUser

Bespoke authentication module 'RemoteUser' uses HTTPServletRequest.getRemoteUser() to acquire username from tomcat after user has been authenticated by SSO. 

Point your SSO at /repository/remoteuser-login

Added files: 
dspace-api/src/main/java/org/dspace/authenticate/RemoteUserAuthentication.java
dspace-xmlui/dspace-xmlui-api/src/main/java/org/dspace/app/xmlui/aspect/eperson/RemoteUserAuthenticateAction.java
dspace-xmlui/dspace-xmlui-api/src/main/java/org/dspace/app/xmlui/aspect/eperson/RemoteUserLogin.java

Modified files:
dspace-xmlui-api/src/main/resources/aspects/EPerson/sitemap.xmap
dspace-xmlui-webapp/src/main/webapp/sitemap.xmap

System changes: add the parameter tomcatAuthentication="false" to the ajp connector in /opt/tomcat6/conf/server.xml 

Tested and working in Dspace 1.8.2