Create a config setting to disable labels in ThumbnailNavigation

[mejackreed]

We are setup to do this already just need to poke everything through.

Came up on the 09/03/2020 community call proposed by @surreal8

[cbeer]

I tagged this as low-hanging fruit because it should be relatively straight-forward, with one minor wrinkle:

• add a new setting in the settings.js (which gets merged into the provided configuration and presented as the config stem in redux)
• connect the config setting to a prop in ThumbnailNavigation(presumably)
• and the wrinkle: there's a lot of intermediate components between the ThumbnailNavigation panel and the actual thumbnails, including some indirection from react-window.