Added day of week and year/month/day to digital.

Adds internationalized day of week, month, day of month, and year
to the sample digital watchface.
Listens for Locale changes in order to update the date formatter
objects in the digital watchface.

Bug: 21299339
Change-Id: I7216dbfaa6a7009acf99c9437fc3c6f0a234660d