Add a widget: table with hierarchy

There is a handy view which is used, for example, in the Mac OS X finder (and OmniOutliner.app in the Pro version), which combines a table view of several columns across with the ability, in the first column, to open up the subtree underneath the given row.

Example uses

• Exploring files in their pod, the user wants as an alternative to the current folder view which old has outline mode with no columns.

• Listing tasks in a tracker, when tasks can have sub-tasks. Currently you can create subtasks individually, but the user wants to be open up tasks to see their subtasks in the issue table view

• If we support groups within other groups in the Contacts, this widget would be able to list an outline mode list with the number in each group.

There may be all kinds of other uses.

El issue describe un widget de tabla jerárquico, pero no indica ningún archivo de implementación, prueba ni punto de entrada. Primero hay que aclarar el alcance del widget y qué vistas existentes de tabla, carpetas, tareas o contactos debe admitir. La tarea estaría terminada cuando hubiera un diseño acordado y una implementación funcional para el caso de uso seleccionado.