Moved build_indexed_dataset from tests/C/query/common to tests/suite/programs and renamed it to build_standard_dataset, since it's generic and will be used in non-query-related tests later.
Made dataset listing/ID matching/etc. in build_standard_dataset more generic using a list of name-builderfunction pairs.
Renamed the datasets in build_standard_dataset to have more informative names and descriptions,
renamed the queries in tests/C/query/query-xmls, and added more messages to 19_query.sh.