Fix ajax on add menu item boxes

[koopersmith]

The ajax that switched between add menu item tabs was broken and causing a reload.

The patch fixes switching between tabs, but clicking on links to view paged results (in view all) still causes reloads.

(In [14332]) Fix ajax on add menu item boxes. props koopersmith, see #13204

(In [14333]) Clarify menu creation versus save. props duck_, see #13134. Check in scripts for r14332, see #13204.

Paged results still cause reloads, and need to be ajaxified.

(In [14464]) Consolidate nav menu item ajax. Other misc fixes. props koopersmith, see #13204.

Latest patch shifts jQuery extensions into their own function and modifies the addSelectedToMenu extension to make one ajax call instead of one per item.

one.call.multiple.items.1.patch was committed in [14468]

Fixed?

We still need to add ajax for paged results, but since we're using checkboxes it's less of an issue. That said, if a user clicks on a page link they will lose the menu order (as it equates to a no-save, see #13337) so this is probably worth adding for 3.0.

With the AYS now, it's required for 3.0.

Doing ajax pages.

ajaxy-pagification-of-meta-boxes.13204.diff makes the paginated meta-box links ajaxified.

(In [14943]) Ajaxify pagination requests in menu boxes. Props filosofo. fixes #13204