title: a way to have django SITEURL constant in settings.py
body: <p>I am from PHP background, and I know that constants can be accessed at most of places in a framework and I think it is same in django as well. I tried to have that URL too in django but I tried to have it from django.contrib. I tried to utilize django's Site class and imported that. But the problem is that at time of loading settings.py I can't import any django contrib. file. </p>
  
  <p>So how can I have SITE URL automatically that I can use anywhere, in template as well as at other places.What is the best way to do so? Do any python utility can do so? </p>