Feature Request: iCloud Settings Backup

### Feature Request

With the addition of community videos (which require custom links) as well as the addition of numerous other ways to modify settings in Aerial, I would like to recommend the addition of iCloud Backup support for settings.

This would allow for a few useful things:
1. Any time a computer is wiped and Aerial is installed again, the user can be prompted to restore settings.
2. A user that wants to keep Aerial consistent across multiple Apple Devices could sync the settings across all devices.
3. When community videos are purchased, the link is given in a temporary manner. This means that there's no way to get back to the link should they be disassociated in the future. Having a backup would save these links in iCloud

Thanks!

P.S. It should be noted that if this is implemented, I would not expect iCloud backup of the videos themselves, just the settings text. Additionally, DropBox support could be warranted here as well, but I think should be secondary given how small the settings file would be. Even a free iCloud account should be able to support that.

Start by locating how Aerial stores its settings and review the requested iCloud backup and restore behavior. Done would mean backing up and restoring settings text, including community-video links, without backing up the videos themselves; cross-device consistency is also requested.

Written by the indexing model from the issue text.