Profiles: Fix unread discussions to reflect viewer, closes #1846
Merge branch 'stage' of github.com:vanilla/vanilla into hotfix/profileunread

Conflicts:
	applications/vanilla/models/class.discussionmodel.php
Fix merge error in 2a58389ad1073555781deb672fbc0c5d997931f2
Merge pull request #1869 from vanilla/hotfix/profileunread

Profiles: Fix unread discussions to reflect viewer, closes #1846