bugfix: schemas/util.sql: derived_col_expr_from_check_constraint(): need to handle strs with \n after IS DISTINCT FROM

inputs/.TNRS/schema.sql: taxon_match: put matched-taxon derived columns before accepted-taxon derived columns

inputs/.TNRS/schema.sql: taxon_match: added derived column "[matched_]species[_binomial]~(Accepted_)__@TNRS__@vegpath.org"

inputs/.TNRS/schema.sql: _matched_has_accepted: renamed to matched_has_accepted because the leading _ did not create vertical alignment anyway, due to different quoting syntaxes

schemas/util.sql: added derived_col_name_from_check_constraint()

schemas/util.sql: derived_col_update(): add steps to rename column

web/username_prefix.php: transposes: removed recommendation for vertical alignment because different quoting syntaxes, etc. make it difficult to have a consistent alignment anyway

bugfix: schemas/util.sql: derived_col_update(): don't set_comment() until CHECK constraint exists so that we can use its canon-ed formula

bugfix: schemas/util.sql: check_constraint_expr_enable(): don't remove suffix without also removing prefix. this is done by using extract_by_regexp() instead. also changed check_constraint_enabled() to use regexps to match this.

bugfix: schemas/util.sql: extract_by_regexp(): needs surrounding COALESCE in case no match