[ticket/9492] Retain custom ranks and avatars when setting users default group

PHPBB3-9492
[ticket/9492] Add unit tests for custom ranks and avatars

PHPBB3-9492
[ticket/9492] Fix undefined user_avatar_* values when updating the group avatar

PHPBB3-9492
[ticket/9492] Ensure to update all avatar values when the avatar is changed

PHPBB3-9492
[ticket/9492] Ensure to delete the avatar/rank data when we change it

PHPBB3-9492
[ticket/9492] Fix typo in SQL query

PHPBB3-9492
[ticket/9492] Fix missing phpbb_container in unit tests

PHPBB3-9492
Merge remote-tracking branch 'remotes/nickv/ticket/9492' into develop

# By Joas Schilling
# Via Joas Schilling
* remotes/nickv/ticket/9492:
  [ticket/9492] Fix missing phpbb_container in unit tests
  [ticket/9492] Fix typo in SQL query
  [ticket/9492] Ensure to delete the avatar/rank data when we change it
  [ticket/9492] Ensure to update all avatar values when the avatar is changed
  [ticket/9492] Fix undefined user_avatar_* values when updating the group avatar
  [ticket/9492] Add unit tests for custom ranks and avatars
  [ticket/9492] Retain custom ranks and avatars when setting users default group