Override convert_standalone_image

[Delivers #62973860 #62973874]
Issue pull request for branch centered-image-no-caption-62973860

[Delivers #62973860](https://www.pivotaltracker.com/story/show/62973860)
[Delivers #62973874](https://www.pivotaltracker.com/story/show/62973874)
[Delivers #62973876](https://www.pivotaltracker.com/story/show/62973876)
[Delivers #62972972](https://www.pivotaltracker.com/story/show/62972972)