added "list users" call
added more parameters to list users and a test
added DELETE USER
added test for DELETE USER
improved test for DELETE USER and fixed the bug in the method
deleting user by ID (cleaner way)
added /api/user/modify by id
added is_admin property (so that only admins can manage users via API)
improved test and fixed bugs with is_admin
added migrations
added commit to modify user
Merge pull request #172 from StarterSquad/feature/278-3-implement-admin-access-with-the-right-to-manage-users

Feature/278 3 implement admin access with the right to manage users