Resolve ambiguity of prov:used

[vcharpenay]

In SHACL specifications for actions/behaviors (see #116), prov:used is a relation between a time interval (the action that occurs) and a Web form (that was filled in for the action to start). The relation between the action and the form should be more specific than what is provided in the PROV model.

In the crud-actions scenario, I suggest to introduce the hmas:initiated property (<someForm> hmas:initiated <someAction>). But the relation is likely to be more specific.

[FabienGandon]

we need a dedicated heartbeat meeting with @vcharpenay to discuss that issue ; we keep prov:used until then