Documentation should clarify how the placement works on a dynamic port

The documentation for `IfcDistributionPort` states:

> The placement shall be relative to the nesting IfcDistributionElement, IfcDistributionElementType, or enclosing IfcDistributionPort.

This is great for regular ports.

Dynamic ports do not use a nesting relationship. They use the often questioned `IfcRelConnectsPortToElement` relationship.

For dynamic ports, is the placement also relative, or is the placement not relative?

Given that questions about IfcRelConnectsPortToElement tend to crop up again and again, it would also be good to state some common examples of dynamic ports in the documentation. I'm not an MEP expert so I have no idea what these are :)

My proposal would be to also specify that the placement is also relative. This is more consistent with the rest of the ports.