Added a setDomNodeContents() helper method.
Cannot typehint on DOMNode since $node in this case is actually DOMElement.
Fixed variable misname.
Merge branch '8.x-1.x' into dom-replace-method

Conflicts:
	lib/Drupal/entity_embed/Plugin/Filter/EntityEmbedFilter.php
Use protected for setDomNodeContent().
Merge pull request #11 from drupal-media/dom-replace-method

Added a setDomNodeContent() helper method to simplify process().