Add initial preferred APN feature

 -Add a new column "preferred" to the carriers database for initial
  preferred APN setting.
 -In multi-sim scenarios, each sim will have its own preferred APN
  setting.
 -Bump carriers table version to 9.
 -Add preferred column when upgrading table to version 9.

Change-Id: Iad319ce371ced7e17ac6db1aaedd5c6e14da1cba
CRs-Fixed: 569452