This reverts commit d66148ef39, reversing
changes made to cdb64a81a8.
This change needed to be reverted,
because not enough email clients support inline images.
This adds the functionality of replacing all images that were uploaded
to gitlab with inline images(base64) in emails.
This change fixes the broken images in emails that 7.8 introduced
Rationale:
* In this notification email, the message is the most important content.
It should not be dimmed or smaller than the rest of the text.
* Now that all UI elements are removed, the message *is* the email. It
should be written as a standard email message, without styling.
