db_tool: check return value from controller->run()

- If the controller returns an error object, dump it to the screen,
  along with instructions to run the script with '--help'
DBTool: issue #166; remove connecting to database check

- Moved database `connect()` check into the `BUILD` method for
  _idGamesDB_, so that code block in _DBTool_ is no longer needed
- Return an _Error_ object if no output option was used on the command
  line
idGamesDB: close #166; move connect() call into BUILD