[ticket/13225] Use passwords manager instead of phpbb_hash in migration

PHPBB3-13225
[ticket/13225] Prefix converted passwords with $CP$ in phpBB 3.0.5-RC1

PHPBB3-13225
Merge pull request #3077 from marc1706/ticket/13225

[ticket/13225] Use passwords manager instead of phpbb_hash in migration
Merge branch 'prep-release-3.1.0' into develop-ascraeus