[ALOY-995] Support turning off iCloud backup for auto-generated model databases

As a developer, I'd like to be able to specify that the database generated by an Alloy model not be backed up to iCloud as part of the model's definition. This functionality is provided now if I install a pre-built database. But it is not implemented for the database file created automatically by the sync adapter. Original reference at https://github.com/appcelerator/alloy/pull/119#issuecomment-41156201 Code for setting this option with pre-built databases is at /lib/alloy/sync/sql.js, approx line 413 db.file.setRemoteBackup(false) As pointed out in http://developer.appcelerator.com/question/174874/alloy-database-model need also to reconcile that models are associated with tables. There should be a logical and sure way to turn on or off iCloud backup for the entire DB.