timelog-0: time spent viewing/editing the data is tracked

[atla5]

Background

• i needed to have some reason to use web workers extensively
• might be an interesting metric/analytic in the future /shrug
• for large datasets this may be a paid or a research activity

Success Criteria

• time spent in the application on a given dataset is tracked by a webworker (in seconds)
• upon the completion of a session, the time_logged variable from store-0: uploaded data is converted to json #3 is incremented