[add] dcm:agent

To annotate ORCIDs specified as dce:contributor and dce:creator individuals where added as instances to BFO:MaterialEntity.

To improve that we will import https://www.dublincore.org/specifications/dublin-core/dcmi-terms/#Agent (which is a term that we also use frequently in definitions) and change the assertions to that class.

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also this class could be used in HDO_00001061 to model the relationship "has participant some agent"