Relative URI copy to clipboard

Origin	emf/engineering.yml 22:5
Uri	engineering://nasdanika/modules/html/modules/emf/issues/uri-copy-to-clipboard-relative
Target	EMF
Workable

Drop-down or a dialog with a base URI field to compute relative URI's. Use of relative URI's may be preferred in models which are intended to be reused and the root URI may change.