Add Additional Group By Options Merged

When organizing a features board based on feature or user story, users should be able to group by more than just by Assignee. For example, when organizing a board view, I'd like to see user stories grouped by feature. Currently, you get separate cards for user stories linked to the same feature.

Though you can see a list of user stories that are related to a feature, having that in a board view would be great for planning product increment/sprints.