Admin Bar: Add View Site/Dashboard links, 'View X' links in the admin, 'View'...

Admin Bar: Add View Site/Dashboard links, 'View X' links in the admin, 'View' action link for terms. New custom taxonomy string: view_item, defaulting to 'View Tag' and View Category'. fixes #17705.

git-svn-id: https://core.svn.wordpress.org/trunk@18194 1a063a9b-81f0-0310-95a4-ce76da25c4cd