schemas/util.sql: added relation_exists()

schemas/util.sql: save_drop_views()/restore_views(): store the view path in addition to the definition so it can be used in restoring

bugfix: schemas/util.sql: in_reverse(): can't use `SELECT *` for composite types because this expands them

bugfix: schemas/util.sql: array_reverse(): can't use `SELECT *` for composite types because this expands them

schemas/util.sql: save_drop_views()/restore_views(): use opaque return type so it can be changed without changing the local var type in functions that use this

schemas/util.sql: force_recreate(): recreate_users_cmds: renamed to restore_views_info since this is now whatever is needed by util.restore_views()

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