Authenticate the local user to the current active Social API implementation and fetch his profile data.

This should be done before any other calls into the API. Depending on the platform this might trigger a blocking dialog for providing login details.

// JavaScript
	Social.localUser.Authenticate (function (success) {
        if (success) {
            Debug.Log ("Authentication successful");
            var userInfo : String = "Username: " + Social.localUser.userName + 
                "\nUser ID: " + Social.localUser.id + 
                "\nIsUnderage: " + Social.localUser.underage;
            Debug.Log (userInfo);
        }
        else
            Debug.Log ("Authentication failed");
    });

// C#
Social.localUser.Authenticate (success => {
		if (success) {
			Debug.Log ("Authentication successful");
			string userInfo = "Username: " + Social.localUser.userName + 
				"\nUser ID: " + Social.localUser.id + 
				"\nIsUnderage: " + Social.localUser.underage;
			Debug.Log (userInfo);
		}
		else
			Debug.Log ("Authentication failed");
	});