Roles/Database: commented out debug log messages

- Clarified how many rows were changed in 'apply_schema'
idGamesDB: issue #152; return Error objects for empty queries

- For `get_file_by_id` or `get_file_by_path` queries that return 0
  rows, return an `Error` object with a `type` of `file_id_not_found`
  or `file_path_not_found`
40-idGamesDB.t: close #152; negative tests for get_file_by_[id|path]

- Moved test todos up to the top of the file