Creator of a group added to group's members-list and user-access policy updated (especially for home group)


**Functionalities implemented:**

1) **At the time of creation of the group, the creator becomes it's member. Script also written to update member's list for existing group nodes.**

   - Files modified:
   
   1) views/group.py
      - Appends user-id to author_set field

   2) commands/update_fields_in_existing_documents.py
      - Script for updating existing group nodes
      - Appends creator's user-id to author_set field at 0th index

2) **User-access policy updated: For "home" group, user can't create/edit any resource.**

   - Files modified:
   
   1) templatetags/ndf_tags.py
      - user_access_policy() tag updated
      
   2) Following templates (ndf/templates/) modified:
      - node_ajax_view.html
      - groupdashboard.html
      - mis_create_edit.html
      - mis_details.html
      - mis_list.html
      - mis_po_create_edit.html
      - mis_po_details.html
      - mis_po_list.html
      - quiz_details.html
      - quiz_list.html 

* **NOTE:** Please run following command: ```python manage.py update_fields_in_existing_documents```