[ticket/11930] Use \phpbb\path_helper for avatar URLs

This will ensure that avatars still properly display on extension pages
supplied via app.php.

PHPBB3-11930
[ticket/11930] Fix tests after adding phpbb\path_helper to avatar drivers

PHPBB3-11930
[ticket/11948] Add second routing file to tests

PHPBB3-11948
[ticket/11948] Allow multiple routing files for extensions

PHPBB3-11948
[ticket/11951] Add MariaDB to supported DBMSes in requirement section.

PHPBB3-11951
[ticket/11951] Add MariaDB to platforms we test on.

PHPBB3-11951
[ticket/11948] Use basename and dirname

PHPBB3-11948
Merge remote-tracking branch 'github-bantu/ticket/11951' into develop-olympus

* github-bantu/ticket/11951:
  [ticket/11951] Add MariaDB to platforms we test on.
  [ticket/11951] Add MariaDB to supported DBMSes in requirement section.
Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/11951] Add MariaDB to platforms we test on.
  [ticket/11951] Add MariaDB to supported DBMSes in requirement section.

Conflicts:
	phpBB/docs/INSTALL.html
	phpBB/docs/README.html
[ticket/11930] Move path_helper in front of optional cache argument

Optional method arguments should be after any mandatory ones.

PHPBB3-11930
[ticket/11930] Modify order of properties to fit constructor method

PHPBB3-11930
[ticket/11930] Update docblock of avatar driver constructor

PHPBB3-11930
Merge remote-tracking branch 'marc1706/ticket/11930' into develop

* marc1706/ticket/11930:
  [ticket/11930] Update docblock of avatar driver constructor
  [ticket/11930] Modify order of properties to fit constructor method
  [ticket/11930] Move path_helper in front of optional cache argument
  [ticket/11930] Fix tests after adding phpbb\path_helper to avatar drivers
  [ticket/11930] Use \phpbb\path_helper for avatar URLs
[ticket/11948] Allow resource importing for routing

PHPBB3-11948
[ticket/11948] Check actual result of routes

PHPBB3-11948
Merge pull request #1801 from nickvergessen/ticket/11948

Ticket/11948 Extensions should be allowed to have more then 1 routing file
[ticket/11916] Remove files from hidden attach list after deletion

The hidden attachment_data list needs to be updated if a file got removed.
This was not done until now and caused a general error after submitting a
post if a file was removed after uploading it.

PHPBB3-11916
Merge remote-tracking branch 'Marc/ticket/11916' into develop

* Marc/ticket/11916:
  [ticket/11916] Remove files from hidden attach list after deletion