Fix some tabbing issues on the post editing screen. Add Media no longer skipped when going backwards from content. Save Draft no longer skipped when going forwards from content.

props adamsilverstein. fixes #23195 and #22933
Link post formats in posts list table. Use a dash for standard, like we do for absence of tags. see #16047 Next: use icons, not text descriptions.
Document the mysterious seventh parameter of add_meta_box().

props wonderboymusic, markjaquith. fixes #17515
Introduce wp_remove_object_terms() and wp_add_object_terms(). No more fetch-alter-update nonsense. Use wp_remove_object_terms() in a few places internally.

props simonwheatley, scribu, ericmann, maxcutler. fixes #15475
Allow Backround Image's "select a file" link to be activated by pressing return on the keyboard.

props adamsilverstein. fixes #22606