- Removed `IsAvailable` (use `IsLocalAvailable` or `IsRemoteAvailable`)

- Changed `GetStream(bool allowLocal = true, bool allowRemote = true)` to `GetStream()`, which will now only search for local data. no remote data.

- Kept the `DownloadImage(bool force = false)` method for now, so plugins can still instruct the core to download images not already present locally if needed, but added doc-comments for which exceptions may be thrown by the methods which plugins (and the core) should watch out for if they're using the method.