title: Completely delete Entity from symfony 4
body: <p>I am learning Symfony 4 and having just followed the guide about databases and doctrine i now have a new entity <code>Product.php</code> with an associated repository <code>ProductRepository.php</code> along with a new table in the DB. I want to now remove this entity/repository and update the database accordingly.</p>
  <p>I thought I could simply remove <code>Product.php</code> and run <code>php bin/console make:migration:diff</code></p>
  <p>However, nothing is getting changed.  Is there some simple list of commands to remove all refs to the entity (I can't see any changes in config files - I am using annotations) or do I have to work out which files were created/modified and then go and manually drop the table.</p>