title: Laravel whereDoesntHave() - multiple OR conditions
body: <p>In Laravel 4.2 I have a model called Product with many-to-many relationshis to other models like Country or Category. I want to filter out products that are "incomplete", which means they have no connected countries or no connected categories. I can use <code>whereDoesntHave()</code> method to filter out one relation. When I use it two times in one query it creates <code>AND</code> condition, but I need <code>OR</code>. I can't find <code>orWhereDoesntHave()</code> method in API documentation. I can't pass multiple relations as arguments because it expects first argument to be a string. </p>
  
  <p>I need something like this:<code>
  $products = Product::whereDoesntHave('categories')-&gt;orWhereDoesntHave('countries')-&gt;get();
  </code></p>
  
  <p>Is there any way to achive <code>whereDoesntHave()</code> with multiple <code>OR</code> conditions?</p>