Fix AM/PM text i18n and clean up keyboard support in time picker

Also updates date picker to use drawable for the header background to
match the implementation in time picker. The time picker background
now supports showing a focused state ripple.

BUG: 17344077
BUG: 16227517
Change-Id: Ida715badb4a151fc16edd91fd4a0dae32953c99e
12 files changed