[gallery]show description of dataset in gallery dropdown(?)

[junlincc]

Currently, when user hover on the dataset name in the gallery dropdown, an HTML title attribute shows up to display the title, in case long title doesn't fit in the dropdown width, which is not quite useful in most cases. As a user, I would like to see more details when selecting a dataset to create new chart. It would be helpful if I can read the descriptions of datasets(added in the Edit dataset modal).

The concerns it, when user actually have a long title doesn't fit. so maybe to show both Title and Description? in tooltip, instead of the title attribute?