Cookie tracking

See https://github.com/sjdirect/abot/issues/41

configuration function visibility is changed because it is necessary
as an argument for class constructor during PageRequesterWithCookies object creation.
https://github.com/ArsenShnurkov/abot/blob/localmess/Abot.Demo/Program.cs#L46
Will not make this change since AbotConfigurationSectionHandler.LoadFromXml() can be called statically.