bugfix: schemas/vegbien.sql: public_validations.validation_views(): need to include views with letters after the query # (eg. _plots_06a_list_of_stems)

schemas/util.sql: removed no longer used to_freq(regclass, drop_if_always_1). use to_freq(regclass) and auto_rm_freq() instead.

bugfix: schemas/util.sql: diff(regclass, regclass): only drop freq column if all tables have all 1s

schemas/util.sql: auto_rm_freq(): accept multiple tables, so the freq column is only dropped if all tables have all 1s

schemas/util.sql: added freq_always_1(regclass[])

schemas/util.sql: added drop_column(regclass[])

schemas/util.sql: added parent(regclass)

schemas/util.sql: try_create(): also handle not_null_violation, which is thrown when trying to add a NOT NULL column to a parent table, which cascades to a child table whose values for the new column will be NULL

bugfix: schemas/util.sql: diff(text, text): also need to cast left_/right_ to base type for the IS DISTINCT FROM filter, because the WHERE clause apparently does not use columns from the SELECT list, even though GROUP BY and ORDER BY do

schemas/util.sql: added to_freq(regclass, drop_if_always_1)