add an icon to ungraded media submissions in gradebook2.
add an icon to ungraded media submissions in gradebook2.

fixes #7405

when a student submits a media submission for an assignment, this
commit adds an icon to it in gradebook2 so that it is easy to see
which students have submissions for the assignment.

test plan:
  * create an assignment that accepts media submissions and create
    a submission;
  * view the submission in gradebook2 and verify that an icon appears.

Change-Id: I79a4ff7bbeaf5547a8e5dd35743534492941bdf5
Reviewed-on: https://gerrit.instructure.com/12515
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

arrivu/hoodemo,tgroshon/canvas-lms,instructure/canvas-lms,antoniuslin/canvas-lms,juoni/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,efrj/canvas-lms,tgroshon/canvas-lms,arrivu/jigsaw-lms,arrivu/qibla-ecampus,efrj/canvas-lms,arrivu/jigsaw-lms,snehakachroo1/LSI_replica,arrivu/hiring-site,SwinburneOnline/canvas-lms,Jyaasa/canvas-lms,greyhwndz/canvas-lms,greyhwndz/canvas-lms,Unow/canvas-lms,juoni/canvas-lms,sdeleon28/canvas-lms,skmezanul/canvas-lms,juoni/canvas-lms,venturehive/canvas-lms,ShreniiNepal/shrenii_lmp,venturehive/canvas-lms,ShreniiNepal/shrenii_lmp,Rvor/canvas-lms,AndranikMarkosyan/lms,merichar/canvas-lms,sdeleon28/canvas-lms,roxolan/canvas-lms,Unow/canvas-lms,HotChalk/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,samuels410/greatlakes-lms,kyroskoh/canvas-lms,skmezanul/canvas-lms,roxolan/canvas-lms,Rvor/canvas-lms,arrivu/hiring-site,instructure/canvas-lms,djbender/canvas-lms,arrivu/arrivu-lms,shidao-fm/canvas-lms,arrivu/qibla-ecampus,wimemx/Canvas,arrivu/hoodemo,arrivu/arrivu-lms,ShreniiNepal/shrenii_lmp,narigone/canvas,eCNAP/CANVAS,arrivu/hoodemo,sli7246/canvas_branch,samuels410/greatlakes-lms,matematikk-mooc/canvas-lms,fronteerio/canvas-lms,eCNAP/CANVAS,samuels410/greatlakes-lms,sdeleon28/canvas-lms,shidao-fm/canvas-lms,instructure/canvas-lms,usmschuck/canvas,icelab/canvas,snehakachroo1/LSI_replica,samuels410/greatlakes-lms,sfu/canvas-lms,arrivu/jigsaw-lms,AndranikMarkosyan/lms,wye0220/shindig-canvas,usmschuck/canvas,va7map/canvas-lms,merichar/canvas-lms,Rvor/canvas-lms,ankithbti/canvas_lms,Jyaasa/canvas-lms,sfu/canvas-lms,ankithbti/canvas_lms,fronteerio/canvas-lms,greyhwndz/canvas-lms,nditech/red-innovadores-lms,wimemx/Canvas,kyroskoh/canvas-lms,greyhwndz/canvas-lms,gbleydon/canvas-lms,HotChalk/canvas-lms,grahamb/canvas-lms,utkarshx/canvas-lms,shidao-fm/canvas-lms,jay3126/canvas-lms,rup/Tarrax,venturehive/canvas-lms,landonwilkins/canvas-lms,rup/Tarrax,wrdsb/canvas-lms,HotChalk/canvas-lms,snehakachroo1/LSI_replica,antoniuslin/canvas-lms,whalejasmine/canvas-lms,grahamb/canvas-lms,matematikk-mooc/canvas-lms,Unow/ins,va7map/canvas-lms,ankithbti/canvas_lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,usmschuck/canvas,juoni/canvas-lms,redconfetti/canvas-lms,Unow/ins,kyroskoh/canvas-lms,SwinburneOnline/canvas-lms,grahamb/canvas-lms,narigone/canvas,nditech/red-innovadores-lms,HotChalk/canvas-lms,eCNAP/CANVAS,instructure/canvas-lms,nditech/red-innovadores-lms,shidao-fm/canvas-lms,landonwilkins/canvas-lms,dgynn/canvas-lms,icelab/canvas,efrj/canvas-lms,antoniuslin/canvas-lms,gbleydon/canvas-lms,whalejasmine/canvas-lms,grahamb/canvas-lms,ShreniiNepal/shrenii_lmp,narigone/canvas,landonwilkins/canvas-lms,leftplusrightllc/canvas-lms,nditech/red-innovadores-lms,utkarshx/canvas-lms,dgynn/canvas-lms,va7map/canvas-lms,arrivu/qibla-ecampus,redconfetti/canvas-lms,sfu/canvas-lms,wimemx/Canvas,leftplusrightllc/canvas-lms,skmezanul/canvas-lms,rup/Tarrax,redconfetti/canvas-lms,fronteerio/canvas-lms,tgroshon/canvas-lms,dgynn/canvas-lms,icelab/canvas,arrivu/arrivu-lms,leftplusrightllc/canvas-lms,redconfetti/canvas-lms,skmezanul/canvas-lms,arrivu/hiring-site,loganrun/pincan,wrdsb/canvas-lms,parbros/red-innovadores-lms,whalejasmine/canvas-lms,whalejasmine/canvas-lms,djbender/canvas-lms,jay3126/canvas-lms,instructure/canvas-lms,snehakachroo1/LSI_replica,gbleydon/canvas-lms,Unow/ins,Rvor/canvas-lms,Jyaasa/canvas-lms,fronteerio/canvas-lms,leftplusrightllc/canvas-lms,tgroshon/canvas-lms,parbros/red-innovadores-lms,wye0220/shindig-canvas,utkarshx/canvas-lms,sli7246/canvas_branch,loganrun/pincan,AndranikMarkosyan/lms,landonwilkins/canvas-lms,va7map/canvas-lms,Unow/canvas-lms,wye0220/shindig-canvas,SwinburneOnline/canvas-lms,roxolan/canvas-lms,sli7246/canvas_branch,instructure/canvas-lms,wrdsb/canvas-lms,sdeleon28/canvas-lms,SwinburneOnline/canvas-lms,grahamb/canvas-lms,Jyaasa/canvas-lms,parbros/red-innovadores-lms,jay3126/canvas-lms,sfu/canvas-lms,efrj/canvas-lms,sfu/canvas-lms,eCNAP/CANVAS,jay3126/canvas-lms,dgynn/canvas-lms,usmschuck/canvas,utkarshx/canvas-lms,venturehive/canvas-lms,matematikk-mooc/canvas-lms,loganrun/pincan,roxolan/canvas-lms,antoniuslin/canvas-lms,wrdsb/canvas-lms,narigone/canvas,kyroskoh/canvas-lms,AndranikMarkosyan/lms,merichar/canvas-lms