schemas/vegbien.sql: public_validations: schema comment: documented how to sync the queries with schemas/vegbien.sql

schemas/vegbien.sql: public_validations.rm_all_queries(): when called with no args, operate on public_validations instead of all schemas, since this is the more common use case (replacing just the output queries, not both input and output)

schemas/vegbien.sql: rm_query_group(): documented that this only removes validations output queries (in public_validations), as it is designed for use in updating all output queries at once from the testing DB

bugfix: *.sql: public.source_by_shortname(): need to wrap it in a nested SELECT because Postgres incorrectly does not constant-fold (inline) it, leading to a slowdown when it is therefore run many times. this is done using the steps at wiki.vegpath.org/Postgres_queries#wrap-function-call-in-nested-SELECT .

schemas/vegbien.sql: source_by_shortname(): documented that it must be run as a nested SELECT, because otherwise Postgres will not inline it. not inlining causes the query to be run for each row in a table of potentially millions, and creates a significant slowdown (eg. >1.5 hours for SALVIAS._plots_06_list_of_plots_with_stem_measurements)

schemas/util.sql: eval2val(): made it STABLE so that functions that use it can themselves be inlined. (Postgres apparently ignores the STABLE qualifier, without warning, if the function contains any VOLATILE statements.)

fix: schemas/vegbien.sql: source_by_shortname(): needs to be declared STABLE so it can be constant-folded and only run once per query. (it had previously been VOLATILE because of constraints imposed on functions that run `SET LOCAL search_path`.)

fix: schemas/vegbien.sql: location: added index on top_plot

fix: schemas/vegbien.sql: location: added index on top_plot

fix: schemas/vegbien.sql: _plots_06_list_of_plots_with_stem_measurements: changed columns to match input query