flask-admin: need to break down into separate chunks the changes added to flask-admin

[nad2000]

Need to break down into separate chunks the changes added to flask-admin and get merged to the upstream repo:

1. request query string passing across the requests;
2. search improvement - search in linked fields, eg, OrcidToken search by the owner's name; + fix: outer join;
3. selection of entry with a composite key.
4. some other minor changes...

Over time these changes got mixed up and the owners rejected overlapping changes. So I might need to disentangle them before pushing them to the upstream repo.