Add turn on/off setting for Lychee in Contacts App.

1) User can turn on/off Lychee, or pick an account to backup and restore
contact metadata in Contacts App->Settings.
2) For now, this option is hidden.
3) When user turns Lychee on in Contacts App, set this account's
sync automatically as true and requestSync, others as false.

BUG 26491409

Change-Id: I063787f1465d965d43907ccc31fd0a7f102797e8