Redesign UI and navigation around the folder view, not filmstrip
Start navigation from root
Sort folders first to improve the folder view experience
Show the first image in place of a subfolder in the folder preview row
Don't allow up/down navigation from files to folders

This cleans up the navigation structure a bit and avoids sticking the
user in folders they didn't meant to enter.
Handle currentIndex in ViewLoader
Replace FileViewPreloader with a more customizable QML-based solution
Add animation to FolderView