SLING-3403 Provide new parameter API

* RequestParameter.getName(): the name of the request parameter
* SlingHttpServletRequest.getRequestParameterList(): List of request
    parameters in HTTP request order
* Adapt SlingHttpServletRequestWrapper and increase API version

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1570135 13f79535-47bb-0310-9956-ffa450edef68