This involves redoing the persistence model, to split general,
account, and folder settings into separate SharedPreference stores.
It also requires some preferences to be moved into UnifiedEmail.
Depends on Ibe2e3f93ec164370535ffc5f5b2409544cc8d36d (UnifiedEmail)
Change-Id: Ie6ec389b5b5d2e7ab1b299d0877811ae716526e2