Update Camera2Basic sample based on feedback during Android App Week.

- Replace android.app.Fragment with v4 support Fragment +
  updated related activity / theme
- Call abortCaptures() to fix bug with multiple image captures after
  pressing the shutter button
- Update copyright dates
- Minor Android Studio warning fixes

Test: Manually ran app before/after changes and verified there were no
regressions.

Change-Id: I735cba5f0d3de091ba86f7fc8d8caf6f8338ebb0