Fetch user roles, and display as Popover on navbar

[ning-y]

Features

• Backend saga now fetches role of user
• Slice of state.session added, 'role'
• Backend saga updates state.session.role
• State.session.role is shown as a popover on-click of 'status button' on right of primary navbar after login

[coveralls]

Pull Request Test Coverage Report for Build 267

• 19 of 27 (70.37%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 32.41%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/components/Application.tsx	2	3	66.67%
src/reducers/session.ts	0	1	0.0%
src/components/academy/Status.tsx	7	9	77.78%
src/sagas/backend.ts	0	4	0.0%

Totals
Change from base Build 259:	0.3%
Covered Lines:	1280
Relevant Lines:	3487

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💛 - Coveralls

[remo5000]

Looks good, can you pass role to the academy NavBar, so that it doesn't show the "Grading" tab when the user is not authenticated?