Thousands of SQL queries in the Element admin

Opening an element for edition took over 4 minutes and caused 15025 SQL queries from my local database, because the Django admin tried to load every Revision, every Repository, every User, every Corpus, every ElementType in this corpus, every WorkerVersion, every Worker, every Revision from those workers, every Repository from those revisions, and every MLClass. We should change most of those foreign keys to raw_id_fields, make them read-only, or remove the Inlines.