Stacking every active banner vertically ate header height when several
were active at once. Only the highest-priority banner renders now; a
‹ 1/N › pager cycles through the rest, and all active banners are still
recorded in the notification-center history so cycled-away ones stay
reachable. Newly registered banners preempt the displayed one only when
they outrank it.
Also fix the startup flow: the restart-required banner (now priority 80)
outranks the model-folders setup warning (60), and the setup banner is
retired once a non-empty folder path is saved.
New banners.pager.* keys translated in all 9 locales.
Will Miao
3b9e8efb3d