[ticket/12324] Correctly create di container if config/ is missing from update/

PHPBB3-12324
[ticket/12316] Add Build Status Icon for develop-ascraeus to README.md

PHPBB3-12316
Merge remote-tracking branch 'Elsensee/ticket/12324' into develop-ascraeus

* Elsensee/ticket/12324:
  [ticket/12324] Correctly create di container if config/ is missing from update/
[ticket/12321] Remove execute bit from ucp_main_subscribed.html and buttons.png

PHPBB3-12321
Merge pull request #2198 from n-aleha/ticket/12321

[ticket/12321] Remove execute bit from ucp_main_subscribed.html and buttons.png

* n-aleha/ticket/12321:
  [ticket/12321] Remove execute bit from ucp_main_subscribed.html and buttons.png
Merge remote-tracking branch 'VSEphpbb/ticket/12316' into develop-olympus

* VSEphpbb/ticket/12316:
  [ticket/12316] Add Build Status Icon for develop-ascraeus to README.md
Merge branch 'develop-olympus' into develop-ascraeus

* develop-olympus:
  [ticket/12316] Add Build Status Icon for develop-ascraeus to README.md
[ticket/12330] Fix create index in db tools on mssql

PHPBB3-12330
Merge remote-tracking branch 'Elsensee/ticket/12330' into develop-ascraeus

* Elsensee/ticket/12330:
  [ticket/12330] Fix create index in db tools on mssql
[prep-release-3.1.0-b2] Update version to 3.1.0-b2
[prep-release-3.1.0-b2] Add migration for 3.1.0-b2
[prep-release-3.1.0-b2] Prepare Changelog
[prep-release-3.1.0-b2] Add changelog for 3.1.0-b2
[prep-release-3.1.0-b2] Prepare development of 3.1.0-b3