Add `itemized_resource.traverse(direction="down_left")`

[BioCam]

missing option in itemized_resource.traverse(direction="down_left")

• renamed accordingly itemized_resource.traverse(direction="down")

-> itemized_resource.traverse(direction="down_right")

[rickwierenga]

wouldn't you want left_up and the other ones as well?

• {up, down} x {left, right}
• {left, right} x {down up}

should be 8 variants

[BioCam]

wouldn't you want left_up and the other ones as well?

For completeness-sake maybe, but I couldn't image a case in which the others would be useful.

I added "down_left" because I have a use case right now and am missing this option :)

[rickwierenga]

@BioCam says: we should split into

• start_position, e.g. left
• direction, e.g. down

raise error when impossible

[rickwierenga]

i extended to support all directions and starting locations. i rewrote the entire method to make this easier. it also fixed the situation where this method was actually hardcoded to 96-item resources before.