[dataimport] remove pg_schema parameter from massive store It can be recovered from the system source's configuration.

[dataimport] remove drop_index parameter from massive store "drop_index=False" also implied not dropping any constraints, in particular foreign keys, which meant any attempt to import entities would fail, because we only add metadata (the entities table) after the entity's insertion.

[dataimport/test] update call to ucsvreader Silences warning: [3.20] 'separator' kwarg is deprecated, use 'delimiter' instead