rose bush cycles: print each cycle's last activity

[matthewrmshin]

(N.B. It is less straightforward to get the first real activity of a cycle.)

[matthewrmshin]

@kaday please review.

[arjclark]

@matthewrmshin - I thought about this briefly when the original issue was raised. Have you considered getting the time of the first "real" activity as something like:

SELECT MIN(time) FROM task_events WHERE event IS "started" OR event IS "submission succeeded" OR event IS "submission failed" GROUP BY cycle;

I don't believe it would have a noticable performance impact if you had python do the joining rather than using the sql query to combine states and events (I can see it being horrific depending on how the join was done)

[matthewrmshin]

Yes, but I think I'll give that a miss for now. Before the big cylc refactor, I think it is wiser to concentrate on the trivial.

[kaday]

All checked and all works fine in my environment.