Bug fixes


**Functionalities implemented:**

**1) Bug in get_preferred_lang() template tag, not resolved yet.. hence commented.**
 
   - File modified:
   
     1) templates/ndf/page_list.html

**2) Bug in get_group_type() resolved**
 
   - Was giving following 
     - ```Error in get_group_type() templatetag: invalid literal for int() with base 10: '[group-name]'```
     
   - Reason behind this: Type conversion of string into int where string doesn't consists of digits
   
   - File modified:
   
     1) templatetags/ndf_tags.py
     
**3) 'userDashboard' url replaced by 'dashboard' url and it's argument list.**
 
   - Files modified:
   
     1) templates/ndf/course.html
     2) templates/ndf/drawer_widget.html
     3) templates/ndf/event_details.html
     4) templates/ndf/file.html
     5) templates/ndf/group.html
     6) templates/ndf/node_ajax_view.html
     7) templates/ndf/page_list.html
     8) templates/ndf/person_details.html
     9) templates/ndf/theme.html
     10) templates/ndf/theme_drawer.html
     11) templates/ndf/uDashboard.html
     12) templates/ndf/userDashboard.html