test reset functionality
fixup @todos in menu_ui.module
cleanup @todo in MenuDeleteForm and link to https://www.drupal.org/node/2310329
Part 4: created issue for @todo in menu.inc to remove backwards compatibility for heading class.
Part 4: Just sentence-ifying @todo
try to fix active link issues
revert system controller changes to fix the tests
Part 4: Just sentence-ifying @todo and adding link to new issue to move LinksTest to menu_link_content module.
Part 4: Just sentence-ifying @todo in LinksTest for re-parenting.
Part 4: Adding issue for @todo in toolbar to use plugin ID instead of title for class.
START PART 5: https://www.drupal.org/node/2301319
apply patch https://www.drupal.org/files/issues/menu-2256521-remove-dead-code.patch
and resolve conflicts with 8.x
remove unused constant MENU_MAX_DEPTH