schemas/util.sql: added restore_views() and use it in force_recreate()

bugfix: schemas/util.sql: save_drop_views(): views must be dropped in reverse dependency order, but returned in forward dependency order

bugfix: schemas/util.sql: force_recreate(): dependent views need to be re-created in forward dependency order. this is done by reversing the dependencies only for save_drop_views().

bugfix: schemas/util.sql: mk_set_comment(): need to use VIEW instead of TABLE for views

bugfix: schemas/util.sql: show_create_view(): also need to include view comment

fix: schemas/util.sql: mk_set_comment(): added ;

fix: schemas/util.sql: show_set_comment(): don't display a COMMENT ON statement if no comment, because this will be appended to table defs, etc. and would create clutter

bugfix: schemas/util.sql: mk_set_comment(): need to handle NULL comment properly

schemas/util.sql: added show_set_comment(regclass)

schemas/util.sql: set_comment(): use util.mk_set_comment()