Cloud-Backed Content Apps

On first run, each content app asks where to store content - options include online accounts and local storage.

When an online account is selected:

1. All the content displayed by the app is stored in the cloud - the online account acts as the master server, and the content app is the client.
2. The app keeps a local cache of online content.
3. When a content item is added to the app, it is uploaded to the online account.
4. Local changes to content items are uploaded.
5. Content items can be added and edited while offline. These are uploaded once a connection is established.
6. The user can select content items to be kept in sync - the app works in the background to ensure that the local copy is always up to date.
7. A setting allows all local content to be kept in sync. This is set to off by default.