Url filtering & Group policies modified regarding join/edit group

1)Url Filtering:- Stop the access  to the private or non-Subscribed Groups Directly by entering the Urls
 like:- is a public group url is entered the group would be shown private group wont be shown this was the case when the user is not logged in 
when user is logged in the url should be filtered based on the creation,public and subscribed rest of the urls would be considered broken or invalid and would be redirected to 404 page
Done in ndf_tags.py file and base.html file

2)if a user tries to join a group without login he would be redirected to login page
3) if a user tries to edit a public group without login he would be redirected to login page
the above two part is done in  groudashboard.html