Fix Database Conficts, Add Conflict Rules

[zfir]

• Start Worker in initManager if there is any pending upload
• Add Conflict Strategy for Database when setting state of a PendingUploads as it is being accessed with multiple Workers
• When initManager, cancel all worker when any state(SUCCEEDED, FAILED, ...)
• Set Backoff Criteria to 10 Seconds
• Remove PendingUploads with UPLOADED state when acknowledging events
• Show notification progress for each uploads