[controller] removed unused imports in usermanagement

vispa/controller/usermanagement.py

@@ -2,16 +2,14 @@
 
 # imports
 from passlib.hash import sha256_crypt
-from sets import Set
 from vispa import AjaxException
 from vispa.controller import AbstractController
 from vispa.models.group import Group, Group_User_Assoc, Group_Group_Assoc
-from vispa.models.project import Project, ProjectItem
+from vispa.models.project import Project
 from vispa.models.role import Role, Permission
 from vispa.models.user import User
-from vispa.models.workgroup import Workgroup, WorkgroupItem
+from vispa.models.workgroup import Workgroup
 import cherrypy
-import json
 
 from itertools import izip
 from inspect import getargspec