Fragmentize ZoneList, which is needed in DateTimeSettings refactoring.

- remove old ZonePicker and rename ZoneList to ZonePicker, as
  the name is really confusing (see LocalePicker)
- Make the new ZonePicker fragment.
- remove dependency toward "ZoneList" class.
-- AndroidManifest.xml does not allow the other components to
   access ZoneList directly, so it would be ok to remove without
   using activity-alias.
-- Noticed there is a significant code duplication between
   DateTimeSettings and DateTimeSettingsActivity. I'll work on it
   later.
- add DateTimeSettingsSetupWizardXL class, which is not used yet,
  but will be in the near future.
-- It is not recognized by AndroidManifest.xml

Change-Id: Id26152a3d560f9e0bd84afdf3e1c5101f0e166b4