allow to search for "auxiliary" objectClasses (i.e. those in ldap_entry_objclasses); allow to return all objectClasses including "auxiliary"; various cleanup

Set flag for hasSubordinates and subschemaSubentry. Strip dynamic attributes
before storing entries in syncrepl.

frontend stuff moved into a database structure, essentially to allow overlays to be processed before database selection; passes all tests (ITS#3080)

slightly rework user/operational attributes handling (including fixing a bug in the logic of the previous change to backend_operational()); cleanup; more improvements to slapo-rwm and back-relay

size exceeds dbcache size by minimizing cache thrashing.