Add modifiedBy

[mdoering]

With the latest scrutinizer being abandoned from the Clearinghouse data model we could consider to transfer the creator and last modifier via created/By and modified/By fields in ColDP so it ends up in the Clearinghouse. We could do this for all entities.

When transferring the person we should then also use a very simple agent/user lookup table that combines id, name, email, orcid & homepage so we can later populate missing users in the Clearinghouse.

Is it worth the effort? It would give credit to all the actual editors in the underlying systems and offer them a way to claim "their" user account in the Clearinghouse

[mdoering]

We now have an accordingToID which is the single concept reference and a new and explicit scrutinizer field for Taxon