Enable web version of email on default

[folked]

As super admin, I would like to see an option to enable the web version of marketing emails on default. Users tend to forget to enable this

[#2]

It for sure would save time and be a good solution, so that it doesn't get missed to activate.
Best way would be to handle it in the email settings with a main toggle.

Only difficulty I see is to fill in the URL and Meta for the Online Version. So this would have to be:

- URL is automatically the subject line (as it is now, when activating it)
- Meta Description is filled in with eighter the Preview Text, first 100 letters of the email or a Default Text defined in the settings.

[#3]

This would be really helpful for us, since it's hidden in Advanced Settings and easy to forget about.