Created a small hook-point for subclasses of ApacheClient

This patch allows for ApacheClient subclasses to get access to the HttpClient and additionally provide a way to customize the execution of the request.

In my case, I had a need to provide an instance of CookieStore as a part of the http request, but there wasn't a clean way of achieving this without basically rewriting the ApacheClient.

Cheers,
Richard L. Burton III