schemas/util.sql: added debug_print_return_value()

schemas/util.sql: diff(text, text): support custom search_path because custom %== operators are usually not in the util schema

schemas/util.sql: diff(text, text): renamed IN params to be different from OUT params to support LANGUAGE plpgsql

bugfix: schemas/util.sql: diff(*): changed from STABLE to VOLATILE because these functions create tables

schemas/vegbien.sql: _plots_04_count_of_plots_in_each_project_in_this_source: added operator %== to match the rows by project_name

bugfix: schemas/util.sql: diff(text, text) and types that use its custom FULL JOIN matching: need to use separate operator %== for determining which records to put on the same row, so that the = filter for identical rows only excludes rows that are actually the same, not all rows with the same keys (which would usually remove all rows)

schemas/util.sql: added operator %== , which returns whether the map-keys of the compared values are the same

schemas/vegbien.sql: synced from DB, which changes the order of the ~type tables

schemas/vegbien.sql: _plots_02_list_of_project_names: added = operator that causes FULL JOIN to only use some columns, so that rows for the same label column are put on the same row in the diff table

schemas/util.sql: diff(): support custom = operator for the table type (to FULL JOIN on only some columns). this requires casting to the base type, to avoid an ambiguity with the default = operator for record.