[SD-1122] Refactoring the check permissions
Merge branch 'feat-privilege' of https://github.com/superdesk/superdesk-server into feat-privilege
[SD-1122] Authorization improvements and added missing privileges
[SD-1122] Unit tests are added for the privileges
Flake8 fix
Some refactoring in auth: check permissions
fix(privileges): make privilege names ui friendly

SD-1124