CAS2 Authentication Plugin
       Parameters include :
        - ticketKey : name of the ticket parameter in the URL
        - appURL : url used to connect to nuxeo when CAS auth is done
          ( can be $NUXEO to let Nuxeo compute the URL)
        - serviceLoginURL : CAS url for login form
          ( can use $CASSERVER to let nuxeo define url according to CasServer header)
        - serviceValidateURL : CAS url for ticket validation
          ( can use $CASSERVER to let nuxeo define url according to CasServer header)
        - serviceKey : name of the service parameter in the URL
     - excludePromptURL : if requested url starts with this value, there will be no CAS authentication
       (you can add multiple exclude path by adding different suffix to the parameter name)