Add functionality: gdf_from_bbox.

[xgerrmann]

No description provided.

[xgerrmann]

@AtelierLibre Would you like to take a look at this? It contains a functionality which I think will be useful.

[AtelierLibre]

@xgerrmann sorry, getting used to working across forks branches etc. I don't have a problem with pulling this in but I think @gboeing needs to comment as he has done a lot of work on tidying up the API and I think if this is to be included it would need to be implemented for the graph module as well.

[gboeing]

Thanks @xgerrmann.

@AtelierLibre an equivalent graph_from_bbox function already exists, so this would help make everything consistent. See here.

[AtelierLibre]

@xgerrmann @gboeing Thanks, I have merged this in.