Add Response.CanClear and Response.Clear()

[lodejard]

bool HttpResponse.CanClear { get{
  true if Response.Body.CanSeek && !ResponseHeadersSent
}}
void HttpResponse.Clear() {
  reset body and headers.
}

[Tratcher]

I think they'd go into Microsoft.AspNet.Http.Extensions.

[Tratcher]

                context.Response.StatusCode = 200;
                context.Response.Headers.Clear();
                context.Response.Body.SetLength(0);