Admin bar tweaks

[nacin]

Per a conversation with Jane, I've cooked up a small series of tweaks to the Admin Bar.

There's actually very little code churn -- I just spaced some things out for readability purposes. This patch:

• Removes 'Dashboard' from the initial dropdown, and makes it a first-level item.

• The 'Dashboard' link becomes 'View Site' when in the admin.

• The 'Edit X' links for posts/pages and tags/categories become 'View X' when in the admin.

In support of this patch, there were two other changes made:

• API: A view_item string has been added for taxonomies.

• UI: A 'View' action link was added to the tags/categories list tables, appended to the end as it is for posts/pages. Basically, we just never had View links, so if we're to add them to the admin bar, they should go here too.

[nacin]

Also closed #17553 as a duplicate as this patch does more.

We can cherry pick from this for 3.2, commit the whole thing, or punt to 3.3 -- the point of these changes were to further the original task of a more useful admin bar, but more so to help deal with the usability around some changes to the admin UI.

[nacin]

Also of note, the current_screen object is identical on edit-tags.php and edit-tags.php?action=edit. I resorted to confirming that the $tag global is an object.

[ryan]

Looks good and works well in my testing.

[nacin]

Sign-off from Jane.

[nacin]

In [18194]:

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.

[westi]

In [18213]:

Only show the Dashboard link if you are logged in. See #17705.

[nacin]

In [18284]:

'Dashboard' should be to the right of 'My Sites' for visual hierarchy reasons. see #17705.