By default, leave all folders closed in tree view of files

[philippconzett]

As a user / file downloader, by default, I'd like to see all folders being closed in the tree view of files in a dataset. Currently, the first folder in the hierarchy (regardless of the number of files it contains) is open by default (see this comment). The problem with this is, e.g., that if there are many files in the first folder, you'd first have to close it (or alternatively scroll down) in order to see the other folder(s), and file(s) not contained in folders, e.g. a README file. For a user, it's more convenient to have a nice overview of all the folders and files not contained in folders. I suggest the default settings for closed/open should be a configuration option.