title: Force django-admin startproject if project folder already exists
body: <p>I want to start new django project in already existing folder and obviously get </p>
  
  <pre><code>CommandError: '/home/user/projectfolder' already exists.
  </code></pre>
  
  <p>Is there some way to force startproject command to create project in an existing folder? I have some important data in that folder and also git folder so I don't want to move it somewhere and then move it back.</p>