show the bad data when we have them
cleaner error handling
the HttpEngine only deals with TypedHttpRequest
Like HttpRequestGet, HttpRequestPost now needs a ResponseHandler
the public HttpEngine interface doesn't need to know the class of the HttpResponse
Allow some queries to not care about the data at all by returning a Void type
only BaseHttpRequest are supported for now
handle the HttpStream as another regular type of output
make the BaseHttpEngine more generic for regular exception handling
we don't need the Ion hack to recover the headers when there is an error