func:toOccupied

toOccupied(rec, checked: true)

Given a site, space, equip, or point rec, get its occupied point. The following algorithm is used to lookup the occupied point:

1. Try to find in equip or parent of nested equip
2. Try to find in space or parent of nested spaces
3. Try to find in site if site if tagged as sitePoint

If there are no matches or multiple ambiguous matches, then return null or raise an exception based on checked flag.