Display Images from the Update Feed in Email Notifications

[#1]

Users are adding screenshots to object updates and tagging users. When the notification comes through to the tagged user, there is no image shown in the email notification and no indication that the message contains an email. 

We would like to be able to see the image in the email notification so the recipients/tagged users can more holistically service that update and prioritize its need based on the full contents of the message in email. 

[#2]

@JesseRe1 for viz