* Indicate while backing up database
* Close migrate connection to db before optimising
* Don't vacuum post-migration
In most cases is probably not needed and can be an optonal user-initiated step
* Ensure connection close on NewMigrator error
* Perform post-migration using migrator connection
Flush WAL file at end of migration
* Make ffmpeg/ffprobe settable and remove auto download
* Detect when ffmpeg not present in setup
* Add download ffmpeg task
* Add download ffmpeg button in system settings
* Download ffmpeg during setup
* Refactor transaction hooks. Add preCommit
* Add BlobStore
* Use blobStore for tag images
* Use blobStore for studio images
* Use blobStore for performer images
* Use blobStore for scene covers
* Don't generate screenshots in legacy directory
* Run post-hooks outside original transaction
* Use blobStore for movie images
* Remove unnecessary DestroyImage methods
* Add missing filter for scene cover
* Add covers to generate options
* Add generate cover option to UI
* Add screenshot migration
* Delete thumb files as part of screenshot migration
