schemas/util.sql: added cluster(), which reclusters each time

schemas/util.sql: cluster_once(): use simpler `LANGUAGE sql` now that we're using util.eval() instead of EXECUTE

schemas/util.sql: cluster_once(): use util.eval() instead of EXECUTE to print the CLUSTER statement (if any) it's using

fix: inputs/.TNRS/schema.sql: taxon_match: cluster the table so the rows are always exported in the same order, even when an UPDATE statement is used to run triggers

bugfix: schemas/util.sql: cluster_once(): need to use just the name of the index, without the schema prefix

schemas/util.sql: cluster_once(): use simpler IS DISTINCT FROM instead of array !=

inputs/.TNRS/schema.sql: added _accepted{genus,specific_epithet} derived column, using the steps at wiki.vegpath.org/Postgres_queries#maintaining-derived-column-formulas-across-column-renames

web/username_prefix.php: remove padding used to visually separate elements: documented that this also removes a leading __ that indicates an internal field

web/links/index.htm: updated to Firefox bookmarks: Quick links: added VegBIEN data dictionary spreadsheet, TNRS data dictionary.

fix: web/username_prefix.php: transposes: changed recommended syntax to y~x@url so that _y~ lines up vertically with [y] paths