[ticket/11306] Introduce phpbb_create_default_container

Extracts default container construction to factory function, removing
boilerplate duplication for container construction.

PHPBB3-11306
[ticket/11306] Add docblocks to all container related functions

PHPBB3-11306
Merge PR #1175 branch 'igorw/ticket/11306' into develop

# By Igor Wiedler
# Via Igor Wiedler
* igorw/ticket/11306:
  [ticket/11306] Add docblocks to all container related functions
  [ticket/11306] Introduce phpbb_create_default_container