Issue #32 - Fix locale sync process

* Provide accuracy on the number of records downloaded
* Roll back if part of a record does not make it to the DB
Issue #32 - Update UI strings (clearer options)
Issue #32 - Handle null response
Issue #32 - Display synced responses as 'Downloaded'

* Create new transmission status - Downloaded
* Insert this status when syncing surveyed locales
Issue #32 - Update responses sync

* In the database, add surveyInstance's local id, not the uuid