Stricter insert/update/delete

[mvorisek]

All DB operations incl. update/insert/delete must honor all model conditions

when a record is saved (inserted/updated), it should be reselected to check if the model conditions still select such model (currently model is reloaded, but no rollback is done if the record cannot be loaded)

before any record is deleted, the record should be selected to test if the model conditions match