Added a synchronous interface to the HttpClient


> Right, I didn't know what do to with that since HttpResponse does not 
> contain any errorCode field. I didn't want to add this field in the 
> class directly because the class is used for server-side code 
> (HttpEndpoint).
>
> So I guess throwing an exception will do for now ?
>
>
What matters here is to have a behaviour that would be compatible with 
the one from HttpRestProxy. But on the other hand, I think the passing 
of error codes enables better practices with regards to error handling. 
I would thus enhance HttpResponse with an HttpClientError member instead.