Updates AlarmClock intent API.

Changes to the AlarmClock intent API based on feedback from Alarm team:

1. s/VOICE_CANCEL_ALARM/DISMISS_ALARM/g - "Cancel" is a bit unclear, so we're
changing it to "dismiss". Also, remove "VOICE_" since we should also add
support for this in multi-modal.

2. Removed DELETE_ALARM - we will likely not complete this for Android M.

3. Removed ALARM_SEARCH_MODE_NONE = "none". Instead, if
EXTRA_ALARM_SEARCH_MODE is missing (and alarm data URI is not given), then:
* If exactly one active alarm exists, it is dismissed.
* If more than one active alarm exists, the user is prompted to choose
  the alarm to dismiss.

4. Add ALARM_SEARCH_MODE_LABEL, which allows searching for alarms by a
(partially) matching label.

5. Add SNOOZE_ALARM for snoozing an alarm, with optional
extra EXTRA_ALARM_SNOOZE_DURATION.

Change-Id: I39502532e54d5f0fe51a8545a4c586615f5e5e89