valgrind: attempt to suppress remaining 64-bit database messages
sml: tag after all the indexing has been done
sml: improve tags around generatability

- split "generate" from "enabled"; the latter is a user decision, the
  first is a consequence of it and - eventually - of "status".
- ensure the file-level "generate" is tagged taking into account the
  target model heuristics encoded by generation_types.
- om: hide the file level tags behind the formatter instead of
  exposing it to the workflow (e.g. generate() instead of
  meta_data_path())