Place non-editor related keymaps together, place animation editor keymaps together, move 'Header' keymap (which had exactly 1 entry) into 'Screen' keymap, move SCREEN_OT_header (for showing/hiding header) into 'Header' keymap. Again, this shouldn't break any key configs, but key configs that contain SCREEN_OT_header will add an entry for this under 'Screen' again. Just a very minor glitch.