Scope and order related grouped artefacts

Modify the related_artefacts_grouped_by_distance
method to accept a scope or array as its single
parameter. This is so that the content API can
request just the live artefacts.

Additionally, preserve the artefact order in each
group by passing the group through the
order_related_artefacts method once again.
Only order related artefacts a single time
Merge remote-tracking branch 'origin/scope-order-related-grouped-artefacts'