Allow different Notification scheme than email notifications

[Viðar Svansson]

Notify uses the project notification scheme to send out notifications. This means that it is not possible to have only Notify notifications and not email notifications. It should be possible to have alternative scheme for emails and Notify so that you can disable email notifications completely for issue notifications.

[Viðar Svansson]

Question about this on Atlassian Answers: https://answers.atlassian.com/questions/146673/in-app-notifications-with-jitter-notify-and-email-this-issue