Use TabLayout in DeskClock activity.

Bug: 18693599
Bug: 22876083

I added a wrapper around ViewPager to transform position index as
necessary when RTL is enabled. The DeskClock activity itself still
manages which tab is selected. I plan to move these logic into a
controller in a follow up CL.

Change-Id: Iebf49db4645367031ea23aab075aa13d39faa119