Fixed issue#32 Harikiri. Supplements fix "issue fixes on user management ..." on Jun 5th 2014 (hertus).
Business rules for this use case:
1. users with ROLE_ADMIN can create modify delete all OTHER users.
2. users with ROLE_MANAGER can create modify delete all OTHER users
   except users with ROLE_ADMIN.
3. users with ROLE_ADMIN or ROLE_MANAGER can browse all users.
4. users with ROLE_USER cannot browse, create, modify, delete
   other users.
5. usage of generic users (like admin) is not encouraged but also
   it isn't prohibited either.