Allow facets to lie outside imaging area
This prepares for https://gitlab.com/aroffringa/wsclean/-/merge_requests/464, and is part of https://support.astron.nl/jira/browse/RAP-22.
This prepares for https://gitlab.com/aroffringa/wsclean/-/merge_requests/464, and is part of https://support.astron.nl/jira/browse/RAP-22.