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

schemas/vegbien.sql: added more ~type tables for plots queries

schemas/vegbien.sql: added public_validations.rm_all_queries(schema), which removes all validations queries in a schema, or in all schemas (useful when recreating validations queries from the DDL export file)

schemas/util.sql: validation_views(): moved filtering out of _validations schemas to validatable_datasources() so that calling this function with no args gives the validation views in *all schemas as one would expect

schemas/util.sql: query_relations(): support passing in an input query instead of an output query, which will remove only in the datasource's schema. (note that it was not clear that passing in an input-side query was not previously supported.)

schemas/util.sql: added schema_regexp(regclass)