* Fix#201: Account archive download
* Export actor and private key in the archive
* Optimize BackupService
- Add conversation to cached associations of status, because
somehow it was forgotten and is source of N+1 queries
- Explicitly call GC between batches of records being fetched
(Model class allocations are the worst offender)
- Stream media files into the tar in 1MB chunks
(Do not allocate media file (up to 8MB) as string into memory)
- Use #bytesize instead of #size to calculate file size for JSON
(Fix FileOverflow error)
- Segment media into subfolders by status ID because apparently
GIF-to-MP4 media are all named "media.mp4" for some reason
* Keep uniquely generated filename in Paperclip::GifTranscoder
* Ensure dumped files do not overwrite each other by maintaing directory partitions
* Give tar archives a good name
* Add scheduler to remove week-old backups
* Fix code style issue
* Add moderator role and add pundit policies for admin actions
* Add rake task for turning user into mod and revoking it again
* Fix handling of unauthorized exception
* Deliver new report e-mails to staff, not just admins
* Add promote/demote to admin UI, hide some actions conditionally
* Fix unused i18n
