[ticket/12448] Allow null as default value for columns

PHPBB3-12448
[ticket/12448] Fix null columns for postgres

PHPBB3-12448
[ticket/12448] Fix null columns for MS SQL

PHPBB3-12448
[ticket/12861] Add event to modify the post, poster and attachment data

PHPBB3-12861
[ticket/12656] Pass user object into all console commands.

PHPBB3-12656
[ticket/12872] Add poster_id to viewtopic_modify_post_row

To allow extension authors to use the poster_id var.

PHPBB3-12872
[ticket/12872] Add poster_id to viewtopic_modify_post_row

Change "rc3" to "RC3".

PHPBB3-12872
Merge remote-tracking branch 'tmbackoff/ticket/12872' into develop-ascraeus
Merge pull request #2651 from nickvergessen/ticket/12448

[ticket/12448] Allow null as default value for columns
Merge pull request #2752 from bantu/ticket/12656

[ticket/12656] Pass user object into all console commands for translation
Merge pull request #2745 from nickvergessen/ticket/12861

[ticket/12861] Add event to modify the post, poster and attachment data

* nickvergessen/ticket/12861:
  [ticket/12861] Add event to modify the post, poster and attachment data