title: scrapy startproject doesn't use designated TEMPLATES_DIR for generating project settings.py
body: <p>When I run scrapy (0.24.6) like this:</p>
  
  <p><code>scrapy startproject -s TEMPLATES_DIR=local_templates_dir my_project</code></p>
  
  <p>I get a <code>my_project/my_project/settings.py</code> that is clearly generated from the package default <code>scrapy/templates/project/module/settings.py.tmpl</code>, not from the template found under my <code>local_templates_dir</code>, which by the way, has the same directory structure as found in <code>scrapy/templates</code>. There are no error or warning messages. </p>
  
  <p>Although the <a href="http://doc.scrapy.org/en/latest/topics/settings.html" rel="nofollow">docs</a> seems to suggest this is the thing to do, the code in <code>scrapy/commands/startproject.py</code> seems to say I can't expect this to work at all. It appears to be hardcoded for the package templates folder. Am I missing something, an environment setting perhaps that would make this work the way I expect? Do I need to write a <a href="http://doc.scrapy.org/en/latest/topics/commands.html#custom-project-commands" rel="nofollow">custom command module</a> just to get the correct settings?</p>
  
  <p>The motivation is simply to have a local project settings template for my team, not a default one requiring that each developer has to update the <code>settings.py</code> manually after running startproject.  Thanks for your help.</p>