Add event status and expose current user rating in event search results.

1. Expose event status. Avoids dealing with client notion of time.

  public enum Status {
    UPCOMING,
    IN_PROGRESS,
    COMPLETED
  }

  Also, now only events that have status COMPLETED may now be reviewed.

2. For past events, the event search cruds now show the current user rating for the event.
For the event crud itself an explicit call to /api/event/&lt;id&gt;/review has to be made.