Organize description and title rendering

[garrettmflynn]

This PR attempts to address #748, but diverges from the suggestions introduced there.

IMO directly using those descriptions as titles is risky because description tends to be a long multi-word string whereas title tends to be fairly concise. Especially with multiple interfaces, this will likely be a lot of large, bolded text to focus on—whereas using the small gray text for descriptions allows for reducing emphasis.

To test out some ideas, though, I've implemented the following:

1. Do not use a title if the description is provided (i.e. only show the file box + description below). Otherwise use a default description about the filesystem path type expected
2. Move the description directly beneath the title if the latter exists