[ticket/12862] Add Border

PHPBB3-12862
[ticket/12862] Resize popups consistently

PHPBB3-12862
[ticket/12937] Do not return false. Return null for get and array() for all.

PHPBB3-12937
Merge remote-tracking branch 'github-bantu/ticket/12937' into develop-ascraeus

* github-bantu/ticket/12937:
  [ticket/12937] Do not return false. Return null for get and array() for all.
Merge pull request #2783 from hanakin/ticket/12862

[ticket/12862] Fix pop-up boxes wraps

* hanakin/ticket/12862:
  [ticket/12862] Resize popups consistently
  [ticket/12862] Add Border