Misc fixes to android wear samples for Coral SDK

1. Target sdk version 21 in manifests
2. Wearable Notifications Sample
  1. Add back JBMR2 support.
  2. Add vibrate permission for JBMR2.
  3. Fix sample name.
  4. Fix color for dark -> light theme change.
  5. Api changes for WearableSupport 1.1
6. Timer and SpeedTracker samples:
  1. Api changes for WearableSupport 1.1
7. Fix some missing files and gitignores for wearable samples after
   gradle refresh.

Bug: 18362461

Change-Id: I38a69e6ead7aecde9f28927e7659a3c503e0bad2
(cherry picked from commit 9d799c27)