[UX] show files in folders when adding directory

[generalmanager]

I'm not sure if this is a device specific problem, but on the (horrible) 4.4 stock rom of an Samsung Galaxy Note II LTE only subfolders are shown, but not files.
I understand that this might be intentional to make it easy for users to find the right folder, but it appears to have the opposite effect.

Users might get confused when they can't see their files, especially if the folder to sync doesn't have any subfolders. In this case the message "empty folder" is shown in the background, which is simply wrong.

This get's especially confusing for (root) users who want to sync for example the DCIM/Camera folder. Those often exist on the internal and external SD card, but as the external one is currently not accessible users might think that they are in the wrong folder and can't access the right one.

[Nutomic]

This is right, however, we'd need file/folder icons to differentiate between them.

Maybe from DocumentsUI.

[generalmanager]

Either icons or we could color the file names in a light grey, which is generally associated with "unavailable" or "can't be used" aka "greyed out". And folders should be shown first, so you don't have to scroll down to find the right folder in between hundreds of files.