Update all Action elapsed times when revising Journal after edit

[WardCunningham]

When editing a long page you can end up with many dozens of Actions in the Journal that have accumulated over hours. But if you hover over these to see how long you have been working, all claim to have been recorded milliseconds ago. This can't be right.

addToJournal computes and formats the elapsed time for the inserted action when it could recompute this for all the actions. We don't in general update times based on a real time clock but in this case we do have the opportunity to quote elapsed times that at least agree with each other.