Allow sort by name reverse alphabetical (mobile)

Hey, engineer on the team working on iOS browse and file list updates here.

We are actually working on reverse sorting for iOS right now!

Unfortunately, this is baked into one of the oldest parts of the app codebase, and isn't just as simple as reversing a collection of items. Those items are fed into the file list from various data providers, and are parsed into sections based on what the current ordering type is.

There is actually one class dedicated to each ordering type! (Name, modified date, filetype, and size.) Each ordering class has to be updated individually to support reverse sorting, and each requires different logic for handling section clustering, various edge cases, and support for the myriad surfaces across the app in which a file list may appear.

We hope to rewrite much of this legacy Objective-C code in Swift at some point and take that opportunity to significantly simplify the architecture of these features so future development is much faster. For now, though, we're only able to confirm that reverse sorting is on the way.