Forklift boxes are moving

Hello all,

tl;dr: forklift boxes are now in boxes.d/*.yaml and you manage boxes.d/99-local.yaml instead of boxes.yaml. Migration should happen automatically but do rebase your open PRs.

Longer explanation: was merged. This change unifies all boxes in a boxes.d directory.

Previously we had:
* config/base_boxes.yaml
* boxes.yaml
* .tmp_boxes/*.yaml

Now we have:
* boxes.d/00-base.yaml
* boxes.d/99-local.yaml
* boxes.d/*.yaml

They're loaded in alphabetical order so you can influence loading. Temporary pipeline boxes are created as boxes.d/80-tmp-*.yaml.

You should now create a boxes.d/99-local.yaml instead of a boxes.yaml. Forklift will migrate the box if needed but if you have open PRs then you should rebase them. While migrating it ignores symlinks which should making switching back and forth possible.

As always: please report any problems you might have.