Should allow viewing files.
In practice, Android fails to find any viewer for every file type I've tried.
We might have to explicitly tell it about mime-types?

Refs !67 (comment 31405)

Attempt to allow the user to view the contents when they are clicked

... hoping this makes it easier to wire this up?
Plus it gives a nice hover animation (which one cannot see
on mobile I suppose)

... and use the classic ("deprecated") version, because that version
works better with icons to the left and right of list items etc.

Adds one "delete" icon per entry in the Magic Folder list view
as per #74.

Removes the static "might contain magic" text each entry in the
magic folder list view had. Closes #70.

Uses correct dividers. Closes #48.

Give modal dialogs slightly less bottom padding.

I believe this was already fixed in a later version of Material Design
Components for the Web - which we don't use because it introduced more
bugs.

Fixes #75.