sql_io.py: put_table(): Moved changing the table of the default value column from Resolving the default value column to Setting pkeys of missing rows, because the table change is only needed in this section

sql_io.py: put_table(): Resolving default value column: Always call sql_gen.remove_col_rename() because it will just pass the value through if it's not a column

sql_gen.py: simplify_parens(): Removed extra simplify_parens() at end because it is done in the final iteration that performs no other replacements, so it is not necessary to also do it explicitly

sql_io.py: put_table(): Replaced limit_ref integer with ignore_all_ref boolean, because it is no longer used as a select statement limit

sql_io.py: put_table(): remove_all_rows(): Corrected "just create an empty pkeys table" comment to "just return the default value column"

sql_io.py: put_table(): mk_main_select(): Removed setting limit to limit_ref⁰, because an empty pkeys table is no longer created when ignoring all rows

sql_io.py: put_table(): Setting pkeys of missing rows: Removed "limit_ref⁰ == 0" check because this code is never reached in that case

sql_io.py: put_table(): Ignoring all rows for unrecoverable errors: Even in multi-row mode, just return whatever the default value or column was, instead of creating an output table containing the default value filled in for every row. This also assists the optimization to skip empty levels of taxonconcepts, because it folds the empty level to that level's parent level rather than creating a whole new temp table with ultimately the same contents.

sql_gen.py: not_false_re, not_true_re: Appended \b to ensure that true/false is only matched as a single word

sql_gen.py: simplify_expr(): Also simplify "NOT false" to true