Merge pull request #1 from drupal-media/8.x-1.x

Add UUID to the embed if it wasn't already there.
Remove all children of the node from the existing DOMDocument.
Loading entities by UUID overrides loading by ID.
Clarified some comments.
Fixed coding standards.
Clarified the comment to add UUID
Clarified filter description in doc string.
Clarified comment.
Replace existing content moved to separate PR.
Merge pull request #7 from cs-shadow/8.x-1.x

Entity UUID preferred over ID and comment clarifications.