[ticket/13133] Allow @vendor_name for includecss

PHPBB3-13133
[ticket/13133] Add unit tests

PHPBB3-13133
[ticket/11863] Grey out unavailable activation methods when emails disabled

Further fall back to USER_ACTIVATION_DISABLE when emails are disabled
but evaluate it at runtime.

PHPBB3-11863
[ticket/11863] Display warning to user because of activation method

PHPBB3-11863
[ticket/11863] Add functional test

PHPBB3-11863
[ticket/13100] Display only confirmation buttons when deleting shadow topic

PHPBB3-13100
[ticket/13197] Also delete group avatar from users that have it set

PHPBB3-13197
[ticket/13197] Test that user's group avatar is deleted by group avatar delete

PHPBB3-13197
[ticket/13253] Fix MCP queue link in active topics search.

PHPBB3-13253
[ticket/13262] Mention htaccess file when updating from 3.0 to 3.1

PHPBB3-13262
Merge pull request #3097 from prototech/ticket/13253

[ticket/13253] Fix MCP queue link in active topics search.
Merge pull request #3098 from VSEphpbb/ticket/13262

[ticket/13262] Mention htaccess file when updating from 3.0 to 3.1
[prep-release-3.1.1] Update version number to 3.1.1
[ticket/13268] Properly append ternary result in get_existing_indexes()

PHPBB3-13268
Merge branch 'ticket/13268' into prep-release-3.1.1

* ticket/13268:
  [ticket/13268] Properly append ternary result in get_existing_indexes()
[ticket/13267] Update Automatic Update instructions to include vendor directory

PHPBB3-13267
Merge branch 'ticket/13267' into prep-release-3.1.1

* ticket/13267:
  [ticket/13267] Update Automatic Update instructions to include vendor directory
[ticket/13262] Mention htaccess file when updating from 3.0 to 3.1

PHPBB3-13262
Merge branch 'ticket/13262' into prep-release-3.1.1

* ticket/13262:
  [ticket/13262] Mention htaccess file when updating from 3.0 to 3.1
[ticket/13248] Use auth provider collection for getting provider

PHPBB3-13248