Active timer to bubble to the top

As a busy user
I want to be able to see at a glance whether I have an active timer and which one it is
So that I can remember to _stop_ my timers #221 and can do so without having to spend 2 minutes looking for the active timer.

## Acceptance criteria
+ [ ] Timer line item bubbles to the top of the timer list when activated

There is an open question for me here on whether the timer should return to its original position once stopped.
I think yes, because once there is a prioritisation feature #283 because we don't want to mess with people's prioritised lists.

I will however, open a separate issue on this as I think it's lower priority for now.
I'm only mentioning it because it may inform the technical implementation (passing parameters of the original 'location' for example).