Address more TODO ISO comments.

(and issues arising from).

@arjclark - please review.
What this did was focus the graph view on a range of cycle times, which were defined by +/- hours about the clicked-on task's cycle time.  It wasn't immediately obvious to me how to update this for cylc-6 (I don't think the GUI knows the cycling mode and how to do cycle point calculations...) so I just commented the lines out to allow quick restoration at a later date.  Does that seem reasonable?