Provide HttpServletRequestWrapper that minimizes effort required to override core data

While the Servlet spec provides an HttpServletRequestWrapper that makes it easy to wrap an existing HttpServletRequest and override a specific method, there's still a significant amount of work needed to fully override all methods that are related to a singe "data item".

For instance, if it's needed to provide different headers for a wrapped request, it's not possible to simply override a single method that provides a collection of headers. Instead no less than 5 methods need to be overridden:

* getHeaderNames
* getHeader
* getHeaders
* getIntHeader
* getDateHeader

Specifically, in the above example it's not exactly trivial to implement getDateHeader. It should theoretically not be needed to provide a custom implementation of this getDateHeader method since the Servlet implementation already has one, but there's no portable way to use that.

If it's needed to provide another URL even more methods have to be overridden (getContextPath, getPathInfo, etc).

It would be great if a wrapper class could be provided that identified a number of "core data" items, such as cookies, headers, locales, parameters, the request method, URL and query String, where for each of which the user could provide that "core data" item by overriding a single method.

All methods that provide derived data would call this single method in their container provided implementations. _(this is loosely based on the concept of AbstractMap in Java SE, where a user only has to implement a minimal amount of functionality in order to have reasonable implementations for all methods of the complex Map interface)_

Start by reviewing HttpServletRequestWrapper and the HttpServletRequest methods listed in the issue, then compare how related data such as headers, URLs, cookies, locales, and parameters are exposed. Done means providing a wrapper design that lets callers override one core-data method while derived methods use it consistently, with the Servlet API behavior remaining portable.

Written by the indexing model from the issue text.