Adds notifications for friending, commenting, and other notifications that used notify_user()
added support for code calling notify_user() to pass data to create notification event object for notification senders. Implemented this for comments.
Merge pull request #6187 from cash/site_notifications_update

Fixes #5861 adds support for site notifications for code that calls notify_user()
Fixes #6030 - Hide group bookmarklet from non-members
Merge pull request #6193 from juho-jaakkola/group_bookmarklet

Fixes #6030 - Hide group bookmarklet from non-members
Revert "Fixes #6030 - Hide group bookmarklet from non-members"

This reverts commit 5a6b259a320256c2f75828193aa8da93eebe226e.

The commit will be added to 1.8 branch instead.