Fix issues for HelpText.AutoBuild configuration (issues #224 , # 259)

[moh-hassan]

HelpText.AutoBuild can't apply setting on HelpText to add AdditionalNewLineAfterOption and other setting.
These setting are applied only when parser raise parsing errors.
This PR fix this bug and fix issue #224 , #259 .
You have a complete control on HelpText configuration in custom help.
Also, new extension methods IsHelp() /IsVersion() is added to simplify checking errors if it have help/version option.

        var parser = new Parser(x =>
        {
            x.HelpWriter = null;               
        });
        var result = parser.ParseArguments<Simple_Options>(new[]{"--help"});
        //generate custom help 
        result .WithNotParsed(errs =>
        {               
            var helpText = HelpText.AutoBuild(result,
                h =>
                {
				    //configure help
                    h.AdditionalNewLineAfterOption = false;
                    return h;
                }
                , e => e);
             //print help screen
            Console.WriteLine(helpText);
             
        });

[moh-hassan]

This PR also fix #414 and #455