Verify email

[alrik]

As the system operator i need to make sure, that users verify their email address before can publish release notes and before they can receive notifications.

Acceptance Criteria:

• A verification email is send upon account registration (with email & password)
• Following the link from the verification email verifies the user.
• An unverified user is not able to publish release-notes
• An unverified user is able* to subscribe for updates
• Only verified users receive update notifications