fix(privileges): prevent users from chaning their privileges

in case user is editing his profile and changes role, privileges
or user_type test if has `users` privilege

SD-1069
fix(users): make user default user type not admin

SD-1091
Merge pull request #399 from petrjasek/feat-privilege

fix(users): make user default user type not admin
Merge remote-tracking branch 'upstream/feat-privilege' into feat-privilege

Conflicts:
	apps/users/services.py