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.
Another important point: we need to reuse a centralized instance of ```DynamoPopup```, it should not be embedded this way like we did for the old ```ToolTip``` because this re-creates ```DynamoPopup``` every time we mouse-over a library item, and then it gets added to the visual tree of the application. If you use ```Snoop``` tool, you can see these ```DynamoPopup``` get add on over time and it can grow to big numbers. Let's try to have a single instance at the ```SearchView``` level and keep it for re-use.

The system manages (or reuses) the centralized tool-tip service for tool-tip display, that is why it does not accumulate over time :)