sql.py: run_query(): Exception parsing: Remove PL/Python prefix from exception message so that the regexps can match at the beginning of the message

sql_io.py: put_table(): Handle sql.InvalidValueExceptions by filtering the value out of all input columns. This will be useful for SQL functions that raise exceptions.

schemas/vegbien.sql: namedplace, plantname: *_unique UNIQUE INDEX: Reordered columns to put rank after parent_id and plantname so that these columns, which are usually input table columns, can be used in a merge join index scan, while rank, which is usually a literal value, can applied as an index filter condition after the merge join

sql.py: distinct_table(): Removed literal values from UNIQUE INDEXes because the query planner did not seem to use them to do a merge join

README.TXT: Maintenance: Full DB: Documented how to test full DB backup

backups/Makefile: Added %.backup/test

README.TXT: Documented maintenance of full DB (back up/restore)

backups/Makefile: Full DB backups: Added vegbien.backup

pg_dump_vegbien: If first arg is "all", dump entire DB. Require a first arg so that Usage message will be displayed if run with no args.

Always output Usage messages to stderr and word-wrap them using `fold -s`