Zen: Remove alarm warnings, color the subhead instead.

- When selecting "None" in the dialog, remove the footer warnings
  about alarms, and associated bits.
- Update subhead text for "None".
- Keep track of how often "None" is used (defined as a user change
  during a visible dialog session) and color the subhead text
  with the warning color until it's been used five times.

Bug:17283115
Change-Id: Ief8a1c557716ec2f581b8338511432d17ac0d371