Story 1401: Language Selector Overlay UI Redesign

Also make some overlay styles more uniform, fix a -1px margin hack so
that the border of the last element in an overlay list (.page-list)
doesn't disappear.

Change-Id: Ib700b810c1d1e10fdac1ae43f25c8e043227e02c
Merge "Story 1401: Language Selector Overlay UI Redesign"