lib/sh/db.sh: pg_dump(): ignore "No matching tables were found" error, using new ignore_err_msg()

lib/sh/util.sh: added ignore_err_msg()

lib/sh/db.sh: pg_schema_exists(): documented that `try` is used to suppress the error exit status

lib/sh/util.sh: stderr_matches(): usage: surrounded command in if statement to indicate what context it would usually be used in

lib/runscripts/file.pg.sql.run, schema.pg.sql.run: support custom options to pg_dump in $@

validation/aggregating/traits/BIEN2_traits/bien3_validations_traits_original_mysql.VegCore.sql: added view names using the steps at wiki.vegpath.org/Aggregating_validations_refactoring#prepend-CREATE-VIEW

validation/aggregating/traits/BIEN2_traits/bien3_validations_traits_original_mysql.VegCore.sql: removed trailing whitespace

schemas/vegbien.sql: public_validations_*: merged into single public_validations schema, with type-specific prefixes for each query, so that datasources can use validations queries from multiple type categories, and so that each datasource doesn't have to indicate which validations output schema it's using

schemas/util.sql: diff_cols(): documented how to run EXPLAIN on the FULL JOIN query

schemas/util.sql: diff_cols(): embed left_query/right_query directly in the main SQL statement, so that the query planner can take the sort order of the queries into account in planning the FULL JOIN (and where possible, use a fast merge join)