Allow setting of cycle rate

[dmarmor]

This is a feature request, not a bug, but it appears that items in the menubar cycle about every 5 seconds no matter what. I think it would be really useful to be able to set that cycle rate. I often use that cycling to create a rudimentary animation to show that something is in progress, and 5 seconds is too slow to visually get that at a glance. Ideally, I'd think it'd be set as a parameter on the cycling lines themselves, maybe something like this:

A | duration=0.5
B | duration=0.5
C | duration=0.5

Any chance of adding that ability?