User storage overview

[Dieule26]

List files using the most storage, sorted by size.
Show file names, types, and the amount of storage they use.

[uhrjun]

For now, there is a global storage overview. I'll consider adding a user tab in it to show a more detailed overview of how much storage the current user is using. Since the crossover of the UI is so high between the two. But the information isn't that actionable without per user storage quota, which is not there yet.

[uhrjun]

#247