CoreData: fix "corrupted database" error during a migration

- This was caused by not moving the "-wal" and "-shm" files around,
  along with the main sql file, during the migration process (e.g. when
  moving the temporary files to the final location)
- Created a new function moveSQLFilesFrom:to:, similar to the
  removeSQLFiles: function that handles the moving of all three in one
  go.