include appropriate JSP 2.0/EL implicit variables in Groovlets

While we're making life easier for the developer we should also add familiar JSP 2.0/el objects where appropriate.

looking at: http://java.sun.com/j2ee/1.4/docs/tutorial/doc/JSPIntro7.html, we see these variables

• param: Maps a request parameter name to a single value
• paramValues: Maps a request parameter name to an array of values
• header: Maps a request header name to a single value
• headerValues: Maps a request header name to an array of values
• cookie: Maps a cookie name to a single cookie
• initParam: Maps a context initialization parameter name to a single value

Finally, there are objects that allow access to the various scoped variables described in Using Scope Objects.

• pageScope: Maps page-scoped variable names to their values
• requestScope: Maps request-scoped variable names to their values
• sessionScope: Maps session-scoped variable names to their values
• applicationScope: Maps application-scoped variable names to their values

Out of these i think it makes sense to have:
param,paramValues,header,headerValues,cookie,requestScope,sessionScope,applicationScope