Showing tooltip with new library view design

Hi, @Benglin, I have added our tooltip to new library design. I have to rewrite tooltip a little bit and use cached information for displaying.
The following can be changed to for better readability :)

```cs
if (this.DataContext is Dynamo.Search.SearchElements.DSFunctionNodeSearchElement)
    cachedDataContext = this.DataContext;
else if (this.DataContext ais Dynamo.Search.SearchElements.NodeSearchElement)
    cachedDataContext = this.DataContext;
```