Fixes message popin excerpt filtering
Validate DeliveryType before setting
Plugins have been using an invalid DeliveryType forever.
Filters inbox popin with htmlspecialchars instead of PlainText
Adds filtering to BodyBox format
Merge pull request #2054 from vanilla/hotfix/security-aug

Filtering improvements
Notifications:  Add event to InformNotifications.
Merge pull request #2073 from vanilla/hotfix/inform-notifications

Notifications:  Add event to InformNotifications.
Merge branch 'master' into stage