[http-client] ENH: Add response as() methods that return HttpResponse wrapping bean, list and stream

[rbygrave]

These allow access to the http status code and headers for success responses that we want as a bean, list of stream.

final HttpResponse<MyDto> response = client.request()
      .path("hello/saveform")
      .formParam("name", "Bax")
      .formParam("email", "Bax@foo.com")
      .POST()
      .as(MyDto.class);           <!-- HERE !!!

// access to status code and headers
int statusCode = response.statusCode();
HttpHeaders headers = response.headers();

// with body converted to the type we desire
MyDto body = response.body();