Breaking up https://github.com/backdrop/backdrop-issues/issues/3639 into some easier chunks.

  • [x] at admin/content/book change the tab title to "Manage books"
  • [x] fix the breadcrumb when at admin/content/book/%
  • [x] Remove the Outline tab on nodes (node/%/outline). We have a "Book outline" vertical tab on the node edit with the exact same form.
  • [x] add a "Remove from book outline" link to vertical tab on node edit.
  • [x] add a "Reorder book pages" link to vertical tab on node edit.
  • [x] Make "Content type for child pages" into select list. admin/content/book/settings
  • [ ] fix entity cache issue when removing node from book outline

Part of META https://github.com/backdrop/backdrop-issues/issues/3639

ADVOCATE: @stpaultim

GitHub Link: 
https://github.com/backdrop/backdrop-issues/issues/5331
GitHub Issue #: 
5331