[ticket/11531] Add basic set of functional tests for new avatar system

This currently includes tests for the gravatar, remote avatar, and upload
avatar drivers. The local avatar driver is currently not supported. Two
tests currently fail and have been marked as incomplete. One failure is
due to an issue with Symfony's DomCrawler that exists in Symfony < 2.2.
The other one is caused by a bug in the way remote avatars are treated.
According to my tests, this bug also exists in phpBB 3.0.11 and has been
reported in the tracker: http://tracker.phpbb.com/browse/PHPBB3-11534

PHPBB3-11531
[ticket/11531] Add acp and ucp groups functional tests for avatars

The test for the acp and ucp groups settings are currently marked as
incomplete due to a bug that causes the settings to not show an error
when incorrect data is entered. However, the avatar data is not saved.
That means that even though the error treatment seems to correctly work,
the user is never informed of the issues with the submitted avatar data.

PHPBB3-11531
[ticket/11531] Use assertContainsLang() where possible

PHBB3-11531
[ticket/11531] Remove incomplete flags for tests after merging PR #1404

Issues should be fixed by the now resolved ticket PHPBB3-11535:
http://tracker.phpbb.com/browse/PHPBB3-11535

PHPBB3-11531
Merge branch 'develop' of https://github.com/phpbb/phpbb3 into ticket/11531
Merge branch 'develop' of https://github.com/phpbb/phpbb3 into ticket/11531
[ticket/11531] Add changes for supporting modified testing framework

Additionally, the groups avatar is deleted after the avatar tests in the
ucp groups page in order to prevent issues with other tests that expect
that no avatar has been set for the admin group.

PHPBB3-11531
[ticket/11582] Add new service for permissions

Replace calls to the language-array type with a call to get_types()

PHPBB3-11582
[ticket/11582] Use new class for categories

PHPBB3-11582
[ticket/11582] Fix event dispatcher class name

PHPBB3-11582
[ticket/11582] Add event in constructor and add docs

PHPBB3-11582
[ticket/11582] Add methods to return the language string

PHPBB3-11582
[ticket/11582] Use new methods and remove duplicated entries

PHPBB3-11582
[ticket/11582] Use member isntead of a new variable everytime

PHPBB3-11582
[ticket/11582] Remove left over calls to lang['acl_*']

PHPBB3-11582
[ticket/11582] Split permission language strings from logic

PHPBB3-11582
[ticket/11582] Fix documentation for adding permissions

PHPBB3-11582
[ticket/11582] Remove useless prefix

PHPBB3-11582
[ticket/11582] Fix missing @params in the doc blocks

PHPBB3-11582
[ticket/11582] Fix missing closing bracket

PHPBB3-11582