Unify data/power layout, confirm disable, round.

Share consistent layout between data usage and battery usage.  Show
confirmation dialog before disabling mobile data.  Round warning/limit
sweep values to match displayed label.  Suppress fade when switching
data usage tabs.

Bug: 5208510, 5058157, 5038589, 5252816
Change-Id: I3c76f3397445d2d3b173666a41672871df4c61af