Feature request: horizontal grouping (swimlanes)

[ctbarrett]

It would be useful to organize a kanban board by grouping cards into horizontal swimlanes by project (bonus points if they were collapsible). Currently I have a single notebook for tasks, and I'm using tags for projects, but I may try using separate notebooks, and filtering projects via notebookPath. In either case, it would be great if I could visually group cards together by project, separately from the workflow states I assign to columns.

In terms of the config interface, I think something similar to the columns: map would work well. Some filters may not make sense in both columns and lanes (e.g. completed makes sense either in a column or a lane, but not both). I could see a few different ways to handle that part: having one dimension take precedence over the other where they intersect, ignoring some tags in the lanes: context, or defining a fixed set of filters that could be used.

Example

lanes:
  - name: "Project A"
    tag: project-a
  - name: "Project B"
    tag: "project b"
  - name: "Group AwesomeSauce Other Stuff"
    notebookPath: "/Tasklist/World Domination (working copy)"