Centralized editing possibilities of the Head section in email templates

[#1]

When you have many master e-mail templates in use, and you need to do a change f ex to styling that is placed in the Head section of the templates, it takes a lot of time to update all templates with the change. If the email templates could have a centralized place where the head section was stored it could be maintained from one place - the whole style config used in the head section for all templates. This makes it easier and faster to maintain the system especially when you have many different templates to maintain.