[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
[ticket/13248] Allow specifying different auth provider in provider collection

PHPBB3-13248
[ticket/13248] Always use provider collection for getting provider

PHPBB3-13248
[ticket/13248] Correctly pass provider name

PHPBB3-13248
[ticket/13248] Use functional framework login method in tests

PHPBB3-13248
Merge pull request #3104 from marc1706/ticket/13248-alt

[ticket/13248] Login functions need to use provider collection for retrieving provider
[ticket/security-164] Sanitize all global variables in symfony_request class

SECURITY-164
[ticket/security-164] Correctly format page_name

SECURITY-164
[ticket/13263] Use prosilver as default style if user's style doesn't exist

If prosilver is not installed for whatever reason, it will be installed by
the newly added migration.

PHPBB3-13263
[ticket/13263] Only install/set prosilver if no style available

Users that have a nonexistent style selectd will revert back to the default
style.

PHPBB3-13263
[ticket/13263] Make sure default style exists and clean up code

PHPBB3-13263
Merge remote-tracking branch 'github-marc1706/ticket/13263' into prep-release-3.1.1

* github-marc1706/ticket/13263:
  [ticket/13263] Make sure default style exists and clean up code
  [ticket/13263] Only install/set prosilver if no style available
  [ticket/13263] Use prosilver as default style if user's style doesn't exist
[prep-release-3.1.1] Add 3.1.1 migration file