Make it easier to set withCredentials=true

[sdeleuze]

Using CORS + setting withCredentials=true in the http request is a quite common need, since it is mandatory for apps with authentication in development mode when your server is running on a port (8080 for example) and AngularDart application on another (3030 for debugging).

withCredentials parameter is available in the deprecated http.request() method, but not on http.post(), http.get() etc. It could be great to allow users to specify a withCredentials named parameter un http.post() and other shortcuts methods.

More details about that in https://groups.google.com/forum/#!topic/angular-dart/8FrOdBoYw-A

[jbdeboer]

And we've now deleted the deprecated http.request() method, making it even harder to set withCredentials.

@markovuksanovic Could you add withCredentials back to Http?

[mvuksano]

@jbdeboer Sounds good.

[sdeleuze]

Thanks !