db/schema/security.sql:

`oq_admin` has full SELECT/INSERT/UPDATE/DELETE access to all tables (not just
delete).
engine2:

Correct a minor semantic error in del_haz_calc.
engine2:

Added a couple of comments to del_haz_calc.
tests/engine2_test:

Added tests for del_haz_calc and del_risk_calc. These functions now have 100%
coverage.