ui.gadgets.sliders: rename slider-pen-tuple to slider-pen.
ui.gadgets.sliders: rename slider-pen-tuple to slider-pen.

bpollack/factor,slavapestov/factor,mrjbq7/factor,nicolas-p/factor,slavapestov/factor,AlexIljin/factor,factor/factor,AlexIljin/factor,bjourne/factor,bpollack/factor,nicolas-p/factor,mrjbq7/factor,nicolas-p/factor,slavapestov/factor,factor/factor,tgunr/factor,mrjbq7/factor,nicolas-p/factor,slavapestov/factor,bjourne/factor,tgunr/factor,tgunr/factor,bjourne/factor,AlexIljin/factor,bjourne/factor,factor/factor,bpollack/factor,bpollack/factor,slavapestov/factor,factor/factor,mrjbq7/factor,bjourne/factor,AlexIljin/factor,nicolas-p/factor,AlexIljin/factor,tgunr/factor,mrjbq7/factor,bpollack/factor,tgunr/factor,nicolas-p/factor,AlexIljin/factor,slavapestov/factor,bjourne/factor,slavapestov/factor,AlexIljin/factor,factor/factor,bpollack/factor,bpollack/factor,factor/factor,bjourne/factor,nicolas-p/factor,tgunr/factor,mrjbq7/factor