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/Auth/Permissions/PermissionService.php

@@ -215,7 +215,6 @@ class PermissionService
      * @param Collection $books
      * @param array $roles
      * @param bool $deleteOld
-     * @throws \Throwable
      */
     protected function buildJointPermissionsForBooks($books, $roles, $deleteOld = false)
     {