Auto recreate data store upon deletion
Change STTwitter pod into following its git repo
Rewrite TDAccount and TDAccountChangeDelegate

1. rename TDAccountSyncDelegate to TDAccountChangeDelegate
2. update controllers to reflect the changes
Add tweetsNoAuthorAssigned method to extract orphan tweets
Update assign tweets logic in account

Additional:
1. add delegate method to catch tweets assignment
2. add author_str_id attribute to Tweet entity
3. refactor tweets delegate logic
Link tweets to authors
Merge branch 'backend/timeline_status'