warn if you are about to run out of disk space

[ralfhauser]

when you do daily snapshot, all of a sudden your virtualbox stops working.

And by then, you will no longer able to delete older snapshots.

Unless you can free other things from your C-Drive, you are stuck.

==> virtualbox, please regularly check available disk space proactively and do a pop-up every couple of hours with a warning to delete older versions of the snapshot

(apparently the snapshots have significantly different sizes, so best to say which ones are particularly big)