Note that the `entry_date` is not changed when restarting a timer

* The `entry_date` is still required in case the timer has been logged
  from another location (the webapp or another application) and the
  this application is unaware of the change. Therefore, it might try
  to start a "paused" timer, when the timer actually needs to be
  started for the first time.

  * Simplifies API calls and prevents unnecessary duplicate calls due
    to state issues.