Re #8638. Use workspace start time for added log.

Not the time when the algorithm is run (a strange choice).
If there's not start time, use the epoch (1990-1-1).
Re #8638. Test for the addition of the start time.
Re #8638. Remove redundant line.

It was just setting the property to the value it already had (since
it's an InOut).
Merge branch 'feature/8638_addsamplelog_starttime' into develop