schemas/util.sql: added col_re()

fix: schemas/util.sql: derived_col_update(): also need steps to drop column, because DROP __ CASCADE doesn't work when there are dependent views

inputs/.TNRS/schema.sql: _accepted_infraspecific{rank,epithet}: use array slice of new _accepted{genus,specific_epithet,infra_{rank,epithet}}, which is simpler than using remove_prefix() in __accepted_infraspecific_label

inputs/.TNRS/schema.sql: "[accepted_]genus__@DwC__@vegpath.org": don't need to use *Accepted_name anymore because _accepted{genus,specific_epithet,infra_{rank,epithet}} is now generated from *Accepted_name

inputs/.TNRS/schema.sql: taxon_match."__accepted_{genus,specific_epithet}": renamed to "__accepted_{genus,specific_epithet,infra_{rank,epithet}}" since this now includes these other ranks as well

bugfix: inputs/.TNRS/schema.sql: taxon_match."__accepted_{genus,specific_epithet}": use "*Accepted_name" instead of "Accepted_species[_binomial]__@TNRS__@vegpath.org" (from "*Accepted_name_species") because Accepted_name_species apparently sometimes does not match the Accepted_name and uses malformed Unicode characters

backups/README.TXT: added backup retention policy

bugfix: schemas/util.sql: derived_cols_export(): also need to first run util.derived_cols_remove() if changing the derived column order

schemas/util.sql: added derived_cols_remove(), which allows derived columns to be re-created in a different order

schemas/util.sql: added drop_derived_col(), which ensures that drop_column() only cascades to views