Contacts: place local contacts in a special local account

Local contacts should be stored in a special account (not the default
one, which has null values for the name, type, and dataset) so that they
are not being taken over by external contact sync services.

Change-Id: Ib7b18d09e32ad3fffaca5edb925602b27a209151
Signed-off-by: Roman Birg <roman@cyngn.com>