[ticket/12529] Use root_path in controller\resolver to check the template dir

PHPBB3-12529
[ticket/12529] Move $phpbb_root_path to the end of the constructor

PHPBB3-12529
Merge pull request #2441 from Nicofuma/ticket/12529

[ticket/12529] Use root_path in controller\resolver to check the template dir

* Nicofuma/ticket/12529:
  [ticket/12529] Move $phpbb_root_path to the end of the constructor
  [ticket/12529] Use root_path in controller\resolver to check the template dir