Do not disturb: persist user config.

Load and store user configuration for do not disturb.  Separate
out service-related aspects into new helper.  Make config availble
over NoMan for settings.

Implement phone + message based filtering (package whitelist for now).

Implement automatic enter/exit zen mode overnight scheduler.

Bug:14211946
Change-Id: Ib28aab0e4c5c9a5fd0b950b2884b1ab618fdfeca