Gracefully handle device out of space for sync or download

[MTRichards]

As an ownCloud user, I want to have my Android device to gracefully handle the case where I am out of disk space so that my device and ownCloud app do not crash when I fill storage with ownCloud synced files

Acceptance Criteria:

• ownCloud monitors amount of free disk space on the iOS device
• New setup for the app to leave empty (default is 500 MB - we can adjust later if that is not enough) - the app will leave 500MB free even when reporting no more free space When the device recognizes that syncing or downloading any additional files requested by the user will cause an "out of space" situation, the user is warned Warning appears as a popup on top of the app, and says "Automatic syncing is disabled because ownCloud is out of free space. Syncing will automatically resume once enough free space is available." Warning has an OK button Once the user removes some files from the device, or changes the "free space" setting above, syncing will resume until the device again finds a free space warning.

@jancborchardt @rperezb

[jesmrec]

Scoped Storage takes care of this. Need some extra research to assure -> new architecture

[jesmrec]

3.0-Beta1. If device runs out of storage, download fails showing snackbar and notification like:

any way to improve this? (showing a more accurate error)