LUN-880 -- replace ability to add new users with the ability of assigning existing users to sites
LUN-880 -- remove the no longer existing view add_user from urls.py (missed this in the prev commit)
LUN-881 -- proper handling of assigning or un-assigning user roles for the current site
LUN-878 -- When the user clicks 'save and continue editing' the current site is taken into account
LUN-878 -- Also look at the request's HOST header for determining the current working site
LUN-880 and LUN-881 -- Added unit tests for testing POSTing user setup formsets
Merge pull request #2 from pbs/bug-fixes

Various bug fixes: LUN-881, LUN-880, LUN-878