[feature request] return edge iterator using topology.all_paths (instead of vertex iterator)

I would like to request the ability to set a flag or an option to return all paths from graph_tool.topology.all_paths() function in the form of edges instead of vertices.

Currently, when there are multiple edges between vertices, seemingly duplicate paths over vertices are returned. In these duplicate paths it is not possible to distinguish which edges were chosen for each path.

This would greatly simplify a lot of tasks we need to do in our project.

Thank you for your continued development of this tool!