Feature/create thumbnail view

[aswallace]

Description

This allows users to toggle between a list view and two different size thumbnail views in the explorer per #69.
The main new component is LazilyRenderedThumbnail, which follows the patterns set by LazilyRenderedRow.
The major logic changes are in FileList (the parent component) which contains the InfiniteLoader component. Note: InfiniteLoader is an external component that only supports lists by default, so needed to add in some customization to accommodate a grid.

Testing

Tested manually and with new unit tests.

• Made sure the row/column to standard index conversion is consistent between view types and the right file stays selected between views
• Different views still work when grouping via the annotation hierarchy
• Using shift or ctrl to select still works as expected with all view types

To do:

There are a couple UX things that would be great to run by someone:

• What do we want the toggle & its icons to look like? Currently they're in the top right near the font size toggle
• Do we want custom icons for different file types (e.g., csv, tiff, czi ?) Right now they all use the same default "no image" icon

Screenshots

Large size thumbnails

Small size thumbnails

Using annotation hierarchy to group

[aswallace]

Made this change since I was having a hard time reading the buttons with the darker background

[SeanLeRoy]

This looks fantastic!! Great job 🎉