OAuth1 simplification

[Lakritzator]

Currently the OAuth1HttpBehaviour is mainly a wrapper and also complicate thing, this might be better implemented via some form of IHttpRequestConfiguration.

The same for the OAuth1HttpMessageHandler, this actually contains its own HttpBehaviour for the special OAuth request and make it impossible to set any specific values for this.

Maybe the OAuth1Settings could be converted to IHttpRequestConfiguration...?
Anyway, the process is currently over complicated! If that was all, I might leave it, but the fact that I'm not sure about the HttpBehaviour inside the OAuth1HttpMessageHandler...

[Lakritzator]

currently the HttpRequestMessageConfiguration is mis-used to pass properties to the OAuth process, I'm not really sure this even works...