Initial commit for tooltip

Tooltip was made as it assumed to be. As it was expected, tooltip covers Scrollbar and user can not use the scroll with mouse until tooltip is opened. Please review code and close that pull request  https://github.com/DynamoDS/Dynamo/pull/2026 because it was made in the wrong brach. I apologize about that wrong pull request, that will not happen again.
The problem is if I write like this:
public class InputParameterTypeConverter : IValueConverter
    {
        private static readonly string NoneString = "none";

        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var input = value as string;
            if (string.IsNullOrEmpty(input) || input.Equals(NoneString))
                return NoneString;

            return ": "+input;
        }
...
}

And use this converter both for Input and OutParameters then Output will be like ": double" and that is incorrect. I should use 2 converters in any case...