Fixed: Use Nzb title as scene name when available

- Use Nzb title as scene name when available
- Only use file name as scene name when its highly likely that it's an actual scene name
- Don't store `DRONE` as default release group in the DB
- Clean up the db removing obviously wrong scene names


Same thing holds here about some releases not having a ReleaseGroup. this is particularly true for p2p web-dl releases, which don't come from the scene.