Refactored NotificationMailSender.

API and calls do not match yet.

Conflicts:
	wiki/src/main/translations/Groups/Translations.en.properties
Notification Mails

- Working hook for mail sending
- Rendering of the template

Conflicts:
	plugins/currikiactivitystream/src/main/java/org/curriki/plugin/activitystream/impl/CurrikiActivityStream.java
	wiki/src/main/pages/Groups/NotificationMailSender.grv
Notification Mails

- Working selection of users by group profile notification settings
- Removed the old DigestMailSender
- Renamed the DigestMailTemplate

Conflicts:
	wiki/src/main/pages/Groups/DigestEmailSender.groovy
	wiki/src/main/pages/Groups/DigestEmailSenderTrigger.vm