Feature/file list ux improvements

[SeanDuHare]

Changes

Some tiny UX improvements I noticed when doing #782

• 106efc5 adds a gradient to the file list when the user has scrolled right or down to the left and top respectively
• 48b01f2 fixes the striped row effect so that rows maintain the same strip while the user scrolls (which previously would flicker)
• 6dc1062 adds diagonal scrolling to the file list (previously you had to horizontally and/or vertically scroll)
• 0c00fe7 removes strange little white pixel in the bottom left corner that would occur when a list was loading

Testing

Locally tested - no unit tests but happen to add them if you can think of something