fix: schemas/vegbien.sql: locationevent: added locationevent_place_visit_id index to facilitate joins to place_visit_id in the validations queries

bugfix: schemas/vegbien.sql: source_by_shortname(): documented that in some cases, it is actually a bad idea to use a nested SELECT, because this will prevent Postgres from using an index scan (causing an equally bad slowdown as not inlining in cases where a nested SELECT is required).

schemas/postgresql.conf: log_min_messages: dropped the verbosity back down to the default, to avoid clogging up the logs

schemas/vegbien.sql: locationevent: documented `VACUUM ANALYZE` runtime (20 min)

schemas/postgresql.conf: log_min_messages: show what autovacuum is doing

fix: schemas/postgresql.conf: disable autovacuum_vacuum_cost_delay to avoid stalling autovacuuming due to a concurrent query, as this can prevent autovacuuming from happening altogether (http://vegpath.org/links/#PostgreSQL:%20Documentation:%209.3:%20Resource%20Consumption:%2018.4.4.%20Cost-based%20Vacuum%20Delay)

schemas/vegbien.sql: location: documented `CREATE INDEX plot_source_id` runtime (5 min)

fix: schemas/vegbien.sql: location: added plot_source_id index to provide the equivalent of the location.source_id index for outer plots. this will help Postgres choose the right query plans in queries involving outer plots.

schemas/vegbien.sql: _plots_18_list_of_subplots_codes_for_each_plot_for_each_project: added ~type table

schemas/vegbien.sql: _plots_15_pct_cover_of_each_verb_taxon_in_each_plot_in_each_pro: added ~type table