feat(privileges) - [SD-1122] Authorize the user for the privilege (from role), usertype

There are also schema changes:

* User will have one role instead of list of roles
* Users will have privileges (as well as role)
* Roles will not have inheritance
* Roles now will have privileges
* User type can be either user or administrator

On fetching a single user there will be a field : active_privileges to work out the unified privileges