Feature request: display files as trees

• Transmssion version: 2.94 (d8e60ee44f), RPC: 15
• Tr Web Control version: 1.6.0 beta (20180906)
• Browser name & version: Firefox iOS 24.1

Problem description:

Currently all files in a torrent are displayed as a flat list rather than a tree of nested directories. This makes it hard to manage torrents with lots of files, for example, selecting all files in a directory to disable downloading them can be really unwieldy, especially on touch UIs like iPad.

Ideally files in a torrent would be displayed as a tree, where operations applied to a directory (enabling/disabling download, setting priorities, etc) would be automatically applied to all files within that directory.