Modify Settings page's 3rd pane grid markup for File Extension Details when 4th pane opens

Purpose: To be able to see the details for a particular file extension setting in a fourth pane .

As a staff person
I want to be able to select a particular file extension setting in the 3rd pane results and display its details in a new 4th pane
So that I can understand the scope of the particular setting

Live prototype:
https://xd.adobe.com/view/0bb2d8ab-aabd-4ff6-4d5a-faa59a93368e-7d83/

Brief video walk-through
https://www.dropbox.com/s/3slcv4v49qm92rv/2018-11-06-data-import-19.mp4?dl=0 (see 4:10-5:10 in the video)

Scenarios

1. Scenario 1
   • To allow room for the fourth pane, the third pane results list table format will have less space horizontally on the screen. The third pane will need to change to a static card format or change to the resizable, responsive card format. We will not implement this responsive card design right now. See UIDATIMP-161. Instead, see the horizontal scroll noted in Scenario 2.
2. Scenario 2
   • Given the Data Import Settings/File Extensions result list (04-Settings File extensionsRev1.png)
   • When a User clicks on a particular extension in the results list
   • Then that extension should turn dark grey
   • And a fourth pane should open showing the details of the particular file extension, as shown in the attached 05-Settings File extensions details-Yes.png or 05-Settings File extensions details-No.png
   • And the 3rd pane should have a horizontal scroll bar at the bottom, so that the user can see all of the columns of the 3rd pane. As an example, see the horizontal scroll bar in the 2nd pane of Users or Inventory when a detail record is displayed in the 3rd pane.