Refactored some core entity actions

- Created BookChild class to share some page/chapter logic.
- Gave entities the power to generate their own permissions and slugs.
- Moved bits out of BaseController constructor since it was overly
sticky.
- Moved slug generation logic into its own class.
- Created a facade for permissions due to high use.
- Fixed failing test issues from last commits

app/Http/Controllers/ChapterController.php

@@ -201,7 +201,9 @@ class ChapterController extends Controller
             return redirect()->back();
         }
 
-        $this->entityRepo->changeBook('chapter', $parent->id, $chapter, true);
+        $this->entityRepo->changeBook($chapter, $parent->id);
+        $chapter->rebuildPermissions();
+
         Activity::add($chapter, 'chapter_move', $chapter->book->id);
         $this->showSuccessNotification( trans('entities.chapter_move_success', ['bookName' => $parent->name]));