Ensure admins can circumvent new anonymous marking

[a_craik]

This idea has been developed and deployed to Canvas

This request is in relation to this pending development: https://community.canvaslms.com/community/ideas/priority-double-blind-grading/pages/home 

and the unintended preview of the development experienced briefly in production - see comments here: Canvas Production Release Notes (2018-04-21) 

I would like to suggest a less disruptive way of solving this problem (and expanding on what the problem is):

Problem #1 (recognised by Instructure): anonymous grading can be circumvented by the teacher accessing a specific student submission via the 'more details in SpeedGrader' link in Grades

Problem #2 (not recognised by Instructure): non-teaching staff need to be able to access a specific student submission during anonymous grading for administrative purposes. These staff will not necessarily have the permissions to masquerade as students (the admin tasks required are varied, as are the roles that perform them).

Proposed solution: When anonymous grading is switched on in a course, the 'more details in SpeedGrader' link is hidden to users of role-type 'teacher'/'TA' (and any derivative custom roles). Admin staff can still see and use the link, teachers simply can't (unless anon grading is toggled off).

Comments from Instructure

For more information, please read through the https://community.canvaslms.com/docs/DOC-14928 .