Skip embedded fields in embeddables

This change skips the creation of mapped fields inside embeddables.

Consider the PHP Money class:

```php
public class Invoice {
  /**
   * @var Money
   *
   * @Orm\Embedded(class="Money\Money")
   */
  private $total;
}
```

```php
final class Money implements \JsonSerializable {
   /**
    * @var Currency
    */
   private $currency;
}
```

Here, Money has the mapped field `Currency`. In doctrine Metadata,
this is correctly reflected as `total.currency`.

The EntityRegenerator declares a private field `$total.currency` afterwards.

The changeset suppresses this behaviour by skipping fields containing a
dot as is done a few lines below.

Author: cedricziel

src/Doctrine/EntityRegenerator.php

@@ -76,6 +76,10 @@ public function regenerateEntities(string $classOrNamespace)
             $embeddedClasses = [];
 
             foreach ($classMetadata->embeddedClasses as $fieldName => $mapping) {
+                if (false !== strpos($fieldName, '.')) {
+                    continue;
+                }
+
                 $className = $mapping['class'];
 
                 $embeddedClasses[$fieldName] = $this->getPathOfClass($className);