schemas/util.sql: util.remake_diff_table(): viewing the table in human-readable form: use just the output side's values_() columns, to avoid repeating columns on both sides that are the same and put just the changed columns side-by-side

bugfix: schemas/util.sql: mk_keys_func(regtype): values() function: must be called values_() instead because `values` is a keyword

schemas/util.sql: mk_keys_func(regtype): also add values() function for use in displaying the diff table

schemas/util.sql: mk_keys_func(regtype, col_cast[]): allow changing the name of the generated function

schemas/util.sql: `RAISE USING ERRCODE = SQLSTATE, MESSAGE = SQLERRM`: use simpler `RAISE` to rethrow error

bugfix: schemas/util.sql: mk_keys_func(regtype, util.col_cast[]): use util.create_if_not_exists() to avoid trying to overwrite a custom keys() function the user has written

schemas/vegbien.sql: public_validations: auto-added keys() functions for all queries

schemas/util.sql: diff(text, text): automatically create a keys() function for the base type. this avoids the need to create keys() functions manually for the numerous queries that need them.

schemas/util.sql: added mk_keys_func(regtype)

bugfix: schemas/util.sql: mk_keys_func(regtype, util.col_cast[]): need to handle 1-column records specially, because Postgres does not allow returning a 1-column record when there are OUT params