* develop-ascraeus:
[ticket/12508] Ignore extensions in migration_tips dev tool
[ticket/12508] Fix doc block
[ticket/12508] Add new line to separate the if and foreach better
[ticket/12508] Add a unit test for set_extensions()
[ticket/12508] Only take a list of names for set_extensions()
[ticket/12508] Fix class doc block
[ticket/12508] Move \phpbb\extension\finder to \phpbb\finder
[ticket/12508] Fix usages of the finder
[ticket/12508] Remove extension manager from finder