Improves New Files footer

Makes it display icons for non-image files and keeps the names
from overlapping.

closes CNVS-16865

Test Plan:
  - Enable New Files
  - Open up file preview
  - Icons should show for non-images in the footer
  - The file names should not overlap.

Change-Id: Ia602952d90d7f30d1b9c07e3fdd10ba4a850f8da
Reviewed-on: https://gerrit.instructure.com/44406
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Dan Minkevitch <dan@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: Clay Diffrient <cdiffrient@instructure.com>