modified the user app in the backend to support fitness profiles

backend/.gitignore

backend/secfit/users/models.py

backend/secfit/users/serializers.py

backend/secfit/users/urls.py

backend/secfit/users/views.py

frontend/www/profile.html

frontend/www/scripts/navbar.js

frontend/www/scripts/profile.js

frontend/www/scripts/scripts.js