net4 cproj missing files

[devatwork]

There are some file missing from the net4 cproj file. OAuth1Authenticator.cs is missing for example.

Or is this done on purpose? If not let me know, I will be happy to send a pull request.

[ayoung]

I think that should belong in the proj. Send pull request if possible please.

[pedrolamas]

The problem was not related only with .NET4, but with Silverlight also, so I've already made the necessary changes in #273