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.
I do not think these ```DependencyProperty``` objects are required, we could make use of ```Binding``` in XAML, and then set the tool-tip's ```DataContext``` to point to a ```NodeSearchElement``` object. Have a look at things like how a ```NodeView.xaml``` gets bound to ```NodeViewModel``` object, and how each part of the ```NodeView.xaml``` gets bound to different parts of the ```NodeViewModel``` object.