830 create superadmin mode

[ddey2]

1. show if an user is admin or not on UI
2. Enable admin user to view everything if only the admin_mode is turned on

[tcnichol]

I pushed a small fix in authorizationservice.

Testing it, I can see all users datasets and files with admin mode activated, and when turned off we revert to what it was before.

[tcnichol]

With the last few commits all the issues are resolved and this works. Marking approved.

[longshuicy]

A few things I noticed:

• Once page refreshed, it automatically switch to non-admin mode. Maybe because it's only stored in the redux. Do we want to registered that enable admin mode state to the backend?
• This will also mitigate all the additional parameter needed for every single route
• Search page with admin doesn't work. I can't see other person's resource even though i'm admin
• Lastly, nitpicking... could you add a little bit more vertical padding of the "Admin Mode" in the dropdown to match other items?